Open main menu



Outliner top.png
Please help with verifying or updating older sections of this article. At least some were last verified for version 2.8.

This article is for the PC version of Stellaris only.
Mammalian Citadel

A starbase is the primary space station used throughout the game and is used for determining the ownership of a given star system, construction, repair and maintenance of ships, collection and transportation of Trade Value in addition to it acting as a strategic fortress during warfare.



A starbase's most fundamental function lies in asserting ownership over a star system. Doing so requires fully surveying the desired system and then constructing a starbase in it. The build cost is 100   Alloys and an additional   influence cost on top of that. The influence cost is determined by a fixed cost which is then multiplied by the shortest path of hyperlane jumps (gates and wormholes act as "shortcuts") between the target systems and the empire's closest owned system.

Once built, the starbase will appear orbiting the center point of the system. It cannot be destroyed by any regular means but it can still be dismantled by its owner during peacetime if it is of no more than outpost level (higher-level starbases will need to be downgraded to outpost in order to be dismantled). If a starbase is dismantled, the system reverts back to being neutral and unclaimed and can then claimed by any empire.

Besides the initial influence cost, upgrading the starbase to a higher level above outpost level will cost only alloys. Aside from making the starbase more powerful due to better base stats and the addition of more weapon components, the upgrade also allows the owner to fit the starbase with different buildings and modules to increase its defensive capabilities and improve its contribution to the empire beyond its basic role of system control and defense. One such important module is the   Shipyard which enables the construction of military ships in the starbase. Having multiple shipyards on a starbase allows it to effectively act as a "fleet manufactory" by constructing several ships in parallel, simultaneously. Shipyards build order is independent from the main build order of starbase.

Though it is not possible to design a starbase, its components will be auto-fitted with the latest advanced technology as soon as they are made available (at no additional cost to the owner).

Starbase CapacityEdit

An empire can in theory have as many starbases as their economy can support but an empire can only maintain a limited number of upgraded starbases bigger than outposts. The number of upgraded starbases an empire can support is dictated by the Starbase Capacity and exceeding that capacity will cause all upkeep costs for starbases to increase by +25%   Upkeep for every starbase exceeding the cap. This is an empire-wide modifier, and thus affects all starbases owned by the empire. This modifier also affects the maintenance of any modules and buildings on the starbases. Regardless of their level, each starbase bigger than an outpost occupies only one capacity slot and if the need arises, an empire can always downgrade existing starbases back to outpost level to reduce the number of upgraded starbases to within the cap limit.

The base Starbase Capacity is 3, which can be increased by the following:

  • +1 for every 10 systems owned by the empire
  • +2   adopting the Supremacy tradition tree
  • +2   Stellar Expansion technology
  • +2   Manifest Destiny technology
  • +2   Fortify the Border edict
  • +4   Trading Posts civic
  • +5   Grasp the Void ascension perk
  • +10   Covenant: End of the Cycle
  • +1   Interstellar Expansion repeatable technology (can only be researched 5 times)
  • +2 for each Strategic Coordination Center level, except the site of the megastructure (Total: +6)

Warfare behaviorEdit

Systems with starbases bigger than outposts require a higher influence cost to claim (25 influence). Consequently, those starbases grant a higher war-score if occupied successfully (10 occupation value). An additional benefit of upgraded starbases manifests in their including an FTL inhibitor which, as long as the starbase remains active, prevents enemy ships from leaving the system via any hyperlane other than the one they arrived through. This allows an FTL inhibitor-equipped starbase to turn strategically important systems into efficient choke points, delaying hostile fleets from leaving the system and advancing further by forcing them into an engagement which may last long enough for reinforcements to arrive.

During war, an attacker must disable the enemy's starbase within the system in order to be able to seize control of any planets within said system. As starbases cannot be destroyed, this is achieved by reducing their   Hull points down to 0, disabling them. The starbase will then remain incapacitated for a duration of   30 days (after the latest attack), during which time any military ships in close proximity to the starbase will be able to gain control over it. If the starbase is left unoccupied and is not attacked, it will enter a self-repair phase and become operational again as soon as it regains   5% Hull points. If there are multiple empires fighting on one side of the war, the newly-occupied system will then be assigned to the empire with the strongest claim, even if the system wasn't conquered by them.

Occupied starbases are fully operational and can repair ships of the side that controls it, inhibit FTL for "enemy" ships, and manage defense platforms, all empire-wide bonuses will also be applied, including home territory modifiers (The Eternal Vigilance ascension perk's platform cap of the original owner is also temporarily retained). However their buildings and modules cannot be changed, and they cannot be upgraded or downgraded, although they can be returned back to the owner.

It's worth noting, that auto-upgrading a starbase can "gift" higher tech components to occupied starbases (including FTL inhibitors), while keeping their own more advanced components. They will stay equipped even if said starbase is reclaimed back, so repeated re-conquering might become harder both sides.

Systems containing an unoccupied starbase or unoccupied colonized planets will not be transferred in a forced status-quo peace.


A starbase is auto-fitted with the latest components as soon as they are available to the empire. This is done automatically and has no additional cost for the empire - as such this also does not affect a starbase's level upgrade cost. However, auto-fit does not work well sometimes. Especially with a heavily modded environment adding many new techs and weapons can suffer from that, but it also happens with unmodded games. A player can enforce the commit of auto-fit by upgrading the starbase, build a new module affecting starbase's weapon slots(Gun Battery, Missile Battery, Hangar Bay), or removing one of them.

The weapon slots are fitted with the most effective kinetic and energy weapons (though not necessarily by equal division). The utility slots are divided equally between   shield and   armor components (auto-fitting does not add hull components here), while the auxiliary slot uses standard auto-fitting of a shield capacitor or auxiliary fire-control (whatever is available in order of priority).

Upgrading a starbase requires the technology of the same name and can only be done in sequential order - meaning that if one started with a basic outpost and wants to upgrade it to a citadel, they have to go through every single level in between in order to get to the desired level. Downgrading a starbase, however, reduces its level to the basic outpost level (outpost) straight away - regardless of what level the starbase initially was - and removes any present buildings, modules, and any defense platforms over the outpost's capacity limit. Any resources invested into the starbase prior to downgrading will not be refunded.

Starting from the starport level all starbases can have an   FTL inhibitor onboard if technology is available.

Constructing a new Starbase requires 75   Influence per hyperlane jump from the nearest owned system.

Note: The table lists the base properties of each starbase level. The actual values themselves will differ due to one's progress in-game (technology, tradition, and etc.), existing modifiers (if any) as well as individual starbase composition (buildings, modules, and etc.).

Level   Cost   Time   Upkeep Modules Buildings Platforms   Hull   Armor   Weapons Utilities   Repairs docked fleets
  Outpost 100 100 1 0 0 3 5000 1000   1   2
  Starport 200 360 2 2 1 6 10000 2000   1
  Starhold 500 720 3 4 2 9 20000 5000   1
  Star Fortress 1250 1080 4 6 3 12 40000 10000   1
  Citadel 3500 1440 5 6 4 15 80000 20000   1

Affecting modifiersEdit

Additional modifiers which affect various starbase parameters are summarized below:

Construction and maintenance modifiers
  Outpost influence cost
−50%   Devouring swarm
−40%   Fanatic xenophobe
−30%   Determined exterminator
  •   Xenophobe
  •   Interstellar Dominion
−15%   Expansionist
−10%   Reach for the Stars
  Outpost build cost
−15%   Expansionist
+50% Machine Empire
  Upkeep cost
−20%   Galactic Ambition
+25% "Exceeding starbase capacity" modifier
Upgrade related modifiers
  Upgrade cost
−33%   The Great Game
−15%   Corps of Engineers
  •   Fortifier
  •   Home in the Sky
  Upgrade speed
+100%   Fortress Proclamation
+25%   Corps of Engineers
Military properties related modifiers
+25%   Eternal Vigilance
+20%   The Great Game
  Hull points
+25%   Eternal Vigilance
  •   Gun Battery
  •   Hangar Bay
  •   Missile Battery
  Armor hit points
  •   Gun Battery
  •   Hangar Bay
  •   Missile Battery


A fully upgraded starbase can support up to 6 modules. It is possible to construct multiple modules of the same type and the starbase will be called in the outliner accordingly. Each module costs 50   Alloys, which can be lowered by the following:

  • −25%   Modular Engineering
  • −20%   Home in the Sky
  • −10% "Zero-G Innovations" modifier
Module   Time   Upkeep Effects Requirements Description
  Shipyard 180 1 +1 Shipyard Capacity A Shipyard may build one ship at a time, in parallel with other Shipyards.
  Anchorage 180 1   +4 Naval capacity Fleet anchorages are necessary to support the growth of our navy.
  Gun Battery 180 1
  •   +2 Medium weapon components
  •   +5 Trade Protection
  •   +1 Protection Range
  •   +10% Starbase and Platform armor hit points
  •   +10% Starbase and Platform hull points
Adds two medium-size weapon slots to the Starbase.
  Missile Battery 180 1
  •   +2 Guided weapon components
  •   +5 Trade Protection
  •   +1 Protection Range
  •   +10% Starbase and Platform armor hit points
  •   +10% Starbase and Platform hull points
Adds two torpedo weapon slots to the Starbase.
  Trade Hub 180 1   +1 Collection Range    Gestalt Consciousness A civilian docking area where merchants and traders can conduct business.
  Solar Panel Network 180   +3 Energy   Gestalt Consciousness Advances in solar panel technology cound offset the operating costs of our starbases.
  Hangar Bay 180 1
  •   +1 Hangar weapon components
  •   +10 Trade Protection
  •   +1 Protection Range
  •   +10% Starbase and Platform armor hit points
  •   +10% Starbase and Platform hull points
  Carrier Operations technology Adds a hangar for strike craft to the Starbase.


A fully upgraded starbase can support up to 4 buildings. Unlike modules, it is only possible to construct a single building of any type. Building cost is reduced by −25% by the   Modular Engineering technology.

Building   Cost   Time   Upkeep Effects Requirements Description
  Communications Jammer 50 180 1
  •   –20% Enemy Combat Disengagement Chance in system
  •   –20% Enemy Sublight Speed in system
These powerful jammers interfere with enemy ship-to-ship communications, making it difficult to coordinate fleet movements.
  Disruption Field Generator 100 180 2   –20% Enemy Shield Hit Points in system Generates localized fields of agitated subatomic particles around hostile ships in the system, significantly reducing the effectiveness of their shields.
  Resource Silo 50 180 0
  •   +2000 Resource Storage Capacity
Massive resource silos and energy storage facilities where large quantities of minerals and energy can be safely kept.
  Crew Quarters 50 180 1   –25% Docked ship upkeep    Gestalt Consciousness Provides accommodation and support for spaceship crews, reducing the logistical burden on fleets that are berthed here.
  Crew Gestation Chambers 50 180 1   –25% Docked ship upkeep   Hive Mind The ability to birth and gestate crew drones directly on-site is a logistical boon to local fleets.
  Service Umbilicals 50 180 1   –25% Docked ship upkeep   Machine Intelligence Service Umbilicals connect berthed fleets directly to the core intelligence of the station, allowing it to assist with repairs and refits.
  Fleet Academy 100 360 2   +100 Ship Starting Experience
  •   Interstellar Fleet Traditions
  •   Shipyard
  •    Gestalt Consciousness
For our newly recruited crews to be truly combat ready, they must have capable officers leading them. The Fleet Academy will ensure those officers have up-to-date knowledge on the doctrines and practice of interstellar warfare.
  Battle Simulators 100 360 2   +100 Ship Starting Experience
  •   Interstellar Fleet Traditions
  •   Shipyard
  •   Gestalt Consciousness
Repeated simulation of various battle scenarios will better prepare our shipboard combat drones for real combat.
  Black Hole Observatory 100 360 2   +15 Physics Research
  +1 volitile mote (if Mote Stabilization has been researched)
  •   Subspace Sensors
  •   Star is a black hole
By building a specialized science facility dedicated to studying a black hole, our empire will surely be able to see improvements in our understanding of Physics.
  Colossal Assembly Yards 1000 720 20
  •   Colossus construction enabled
  •   Juggernaut construction enabled
  •   Shipyard
  •   Citadel
  • Colossi or Juggernaut technologies
Abandoning the traditional concept of drydocks, colossal spaceships are assembled by a number of highly mobile independent construction platforms.
  Command Center 250 360 5   +10% Allied Fire Rate in system
  •   Command Matrix
  •   Star Fortress
All system defense efforts are coordinated from this large facility, buried deep within the hull of the Starbase. Map arrays and 3D projections track all space traffic passing through the system at any given time.
  Deep Space Black Site 100 360 2
  •   +1 Unity
  •   +25% System Governing Ethics Attraction
  •   +5 System Stability
  •   The Living State
  •   System is colonized
  •    Gestalt Consciousness
A large part of this Starbase has been set aside as a Black Site that does not officially exist. The entire system is closely monitored from here, while intelligence operatives carefully manipulate local media and social events to the best of their ability.
  Defense-Grid Supercomputer 150 360 2   +8 Defense Platform Capacity   Synchronized Defenses A powerful supercomputer coordinating the relative orbit and firing arcs of the Starbase's defensive platforms, increasing the number of defensive platforms that can be supported.
  Hydroponics Bay 50 180 1   +10 Food   Eco Stimulation By dedicating a section of this Starbase to Hydroponic farming, the station will be able to feed itself and even export excess produce to other systems.
  Hyperlane Registrar 100 180 2   +1 Collection Range
  •   Hyperlane Breach Points
  •    Gestalt Consciousness
Assists friendly ships in the system with FTL travel by identifying ideal conditions for entering the hyperlanes and optimizing projected travel routes.
  Listening Post 100 360 2   +2 Sensor Range
  +4 Hyperlane detection range
  Gravitic Sensors The Listening Post houses a team of dedicated operators tasked with analyzing hyperlane reverberations, functionally extending the range of the Starbase's sensors.
  Nebula Refinery 100 360 2   +10 Minerals
  +1 exotic gas (if Exotic Gas Extraction has been researched)
  •   Mineral Processing
  •   System is inside a nebula
By processing the dust clouds of a nebula, we are able to refine and extract valuable minerals.
  Offworld Trading Company 100 360 0   +2 Trade Value from   Trading Hubs
  •   Space Trading
  •   Trading Hub
The offices of a non-governmental organ dedicated to improving the conditions of interstellar trade.
  Titan Assembly Yards 500 720 10   Titan construction enabled
  •   Titans
  •   Shipyard
  •   Citadel
Specialized drydocks erected on the Starbase's hull allow for the construction of gargantuan Titan-class ships.
  Curator Think Tank 100 360 2   +5 Research    A diplomatic agreement with the Curator enclaves By constructing a research facility entirely focused on learning from, and cooperating with, the Curators, we are able to make significant contributions to our scientific progress.
  Art College 200 360 2   +10 Unity
  •   A diplomatic agreement with the Artisan enclaves
This zero-g Art College, operated in conjunction with the nearby Artisan Enclave, celebrates the beauty of outer space in the works produced by its talented students.
  Trader Proxy Office 100 360 0   -5% Market Fee
  •   System has Trader enclave
  •    Gestalt Consciousness
The Trader Enclave enjoy special privileges on the Galactic Market, which can also benefit us.


Mammalian Ion Cannon

Because starbases are vital targets during warfare, an empire must ensure that they can maintain control over their own starbases to prevent their opponents from seizing control of the system. Investing resources into arming a starbase can allow to function as a strong deterrent to enemy invasions, a powerful supporting power during a fleet battle in the system and a starbase that is heavily armed enough can potentially even repel an entire enemy fleet by itself. Successfully maintaining control over every single starbase in the empire is by itself enough to allow an empire to end the war through a status-quo without losing any systems, earning them a defensive victory.

A starbase's self-defense capabilities can be reinforced with the construction of defense platforms. Defense platforms are smaller military stations that are deployed around the starbase and act as weapons platforms. Defense platforms have two sections for weapon slots which can be outfitted with a wide variety of weapon configurations. They will engage any incoming hostile ships, effectively acting as a supporting weapon, by attacking and distracting them from focusing their efforts on the starbase itself, allowing the starbase to engage the enemies and support the defense platform(s). When compared with ships, platforms are situated between Destroyers and Cruisers classes, their hull and armament slightly better than the former, while their armor-potential is equivalent to the latter. However, due to them having no   Evasion whatsoever, individual platforms are still very vulnerable, and if a strong, sustainable firepower is a priority it is wiser to put more turrets on the base itself and only add in Defense platforms once the starbases available armaments have been maxed out.

As opposed to the auto-fitting of the starbase's components, defense platforms can be altered through the ship designer allowing for several designs to be built based on the different needs in each front and upgraded based on this designs. However, unlike ships, their designs cannot be switched once built, necessitating dismantling and complete rebuilding. It also renders any transferred platforms non-upgradeable. Economically defense platforms are, again, comparable to destroyers, but they cost no alloys upkeep.

Each starbase can support only a certain number of defense platforms based on its level. However, the defense platform capacity can be increased with the following:

  • Globally: +5   Eternal Vigilance, +4/+8/+12  Strategic Coordination Center galactic wonder
  • Locally: +8   Defense-Grid Supercomputer

If all of these modifiers are applied for a total of +25 platforms, a single starbase can support up to 40 Defense platforms when upgraded to Citadel level.

In addition to the regular defense platforms, a citadel-level starbase is also capable of hosting a more powerful platform type that carries a singular weapon, which is stat-wise identical to the Perdition Beam weapon. This means that it is capable of destroying an enemy warship of any size (except for Titans) in a single shot from very far away and cannot be changed. It is titan-class hull-wise, but only battleship-class armor-wise. Economically it is also comparable to the latter without alloy upkeep, and it is deployed quite slowly.

An ion cannon platform is equivalent to 8 defense platforms in terms of capacity slots and can only be constructed on citadel-level starbases.

Defense platform modifiers

Additional modifiers which affect various defense platform parameters are summarized below:

  •   Eternal Vigilance
  •   Secure the Borders
+10%   Synchronized Firing Patterns
  Hull points
+25%   Secure the Borders
  •   Fortified Core Layers
  •   Gun Battery
  •   Hangar Bay
  •   Missile Battery
+500   Improved Structural Integrity
  Armor hit points
  •   Gun Battery
  •   Hangar Bay
  •   Missile Battery
  Build cost
−33%   Fortifier
−15%   Secure the Borders
  Build speed
+100%   Fortress Proclamation