4X (eXplore, eXpand, eXploit, eXterminate) games have seen a meteoric rise in both popularity and playtime over the years as players are growing more accustomed to the genre. With the expanding player base, there are also bound to be more multiplayer games that enable the players to work with each other to either beat the game or their difficult AI opponents.
Some of these games require strict cooperation to face difficult in-game events that can end the game prematurely, while some only have threadbare cooperation gameplay in the form of teams with shared victory conditions. In the end, these games provide an opportunity for the players to work with each other instead of against each other like in the usual gameplay loop.

Thanks to its robust multiplayer system that allows co-op games even with customized empires,Galactic Civilizations 3remains one of the best 4X games for co-op multiplayer even when its age is already showing in some parts of the game. The newest downloadable content it has recently also keeps the gameplay loop fresh for the veterans of the series.
In addition to its multiplayer system, the base game also provides an engaging gameplay loop that keeps the player on the edge while also delivering ahighly engaging storylineto keep the player immersed in the game’s world.

Thanks to its unique multiplayer feature of freezing time whenever combat is happening in multiplayer games,Age of Wonder: Planetfallhas become one of the 4X games that are worthy of being taken a look at whenever a party of friends wants to play a 4X game together in a co-op mode. Although it might require heavy time investment due to its relatively long game time, theengaging gameplay loopwill keep the game fresh for everyone in the co-op game.
Moreover, its tactical combat system benefits from co-op as well, since each of the players can advise each other during the combat phase.

Although the game is entering a relatively old age after being released in 2016,Endless Space 2remains a fan favorite due to its robust gameplay loop and immersive military side of the game, ensuring the players become engaged with the game for a long time. In addition to its amazing gameplay loop,Endless Space 2also has arobust multiplayer systemthat allows all players to simultaneously play a turn without waiting for each other.
Although there are some problems with the game’s relatively old net code that can trigger desyncs during the game, mitigations can be made to ensure the players have a wonderful co-op experience with each other.

Every veteran, new player, and even non-gamers alike has been familiar withCivilization 6thanks to its game’s mainstream popularity. The simple yet deep gameplay loop that can be easily understood but hard to master makesCivilization 6appealing to numerous players, making it easier for players to find others to play for a session of co-op games with a team against other teams or even teams ofhigh-difficulty AIs.
Its turn system allows players to play a turn simultaneously in peacetime, while also giving each player time to use their time well in the allotted turn.

As one of the games that define modern 4X games,Stellarisbecomes a game that is worthy of playing in co-op way due to its complexity in the gameplay loop and engaging narrative design that draws the player into the entirety of the game without getting too overwhelmed or exhausted during the game. Moreover, the game allows multiple players to play seamlessly thanks to its real-time timing which can be paused at any time for flexibility.
Moreover, the game encourages co-op gameplay in multiplayer due to the fact that it is beneficial to survive the galaxy in harmony, except when one of the players is bent onbecoming a Crisisthat looks to end the galaxy.

With the help of thepopularWarhammerfranchise, Creative Assembly manages to create a highly engaging and fun game inTotal War: Warhammer 2in the genre of 4X games which receives positive acclaim due to its engaging gameplay and immersive narrative design. The multiplayer side of the game is also quite accommodating, as it allows both free-for-all gameplay in the head-to-head game mode and specialized co-op gameplay.
With the co-op gameplay, the players need to pick the same faction in order to facilitate seamless multiplayer gameplay while also keeping in tune with the game’s narrative design.

Aging like a fine wine,Sins of a Solar Empire: Rebellionis one of the 4X games that hold up even with its age thanks to its newest expansion and the continual updates that the game receives thanks to the players' and developers' passion for the game. Although the graphics might appear to be dated, the incrediblyimmersive and engaging gameplayand narrative design allow the players to continually play the game.
In addition, the multiplayer side of the game allows co-op gameplay to be relatively smooth for both regulars of the game and newcomers alike. The game also receives continual community support despite the low player base in recent times.