|Designer(s)||Peter Olotka, Jack Kittredge, Bill Eberle, Bill Norton|
|Publisher(s)||Eon Products, Inc, West End Games, Games Workshop Mayfair Games, Avalon Hill, Fantasy Flight Games|
|Players||3–6+ (depending on edition)|
|Setup time||5–10 minutes|
|Playing time||20–120+ minutes|
|Skill(s) required||Prediction, diplomacy, card management|
Cosmic Encounter is a science fiction–themed strategy board game, designed by "Future Pastimes" (collectively, Peter Olotka, Jack Kittredge and Bill Eberle, with Bill Norton) and originally published by Eon Games in 1977. In it, each player takes the role of a particular alien species attempting to establish control over the universe, each with a unique power to break one of the rules of the game. In 1992, a new edition of Cosmic Encounter won the Origins Award for Best Fantasy or Science Fiction Boardgame of 1991, and placed 6th in the Deutscher Spiele Preis. The game was inducted into the Academy of Adventure Gaming Arts & Design Adventure Gaming Hall of Fame in 1997.
Cosmic Encounter is a dynamic and social game, with players being encouraged to interact, argue, form alliances, make deals, double-cross, and occasionally work together to protect the common good. Most editions of the game are designed for three to six players, although official rules exist for playing with as few as three or as many as eight players.
Cosmic Encounter is based on a fixed set of rules which are subsequently modified by other elements of the game.
Each player begins with a color-coded "home system" containing five planets, and twenty tokens representing starships that populate these planets as bases. A central "Warp" is used to place defeated ships for all players. The game goal, in general, is to occupy five bases on planets outside one's home system. The player is dealt a hand of seven cards from the normal card deck, which includes three types of cards normally. Two types are Encounter cards, including numbered Attack cards and Compromise/Negotiation cards, while the third type are "edicts"/"artifacts".
On a player's turn, they retrieve one ship from the Warp, and then turn a card on a second deck, the color-coded "Destiny" deck, indicating which system they must attack. Using a special "attack cone" indicator, the player selects which opponent on which planet to attack, and then places from 1 to 4 ships on the cone. Both the attacker and defender can ask the other players individually to ally with their side, committing up to 4 ships on either side of the conflict.
Once allies have committed to the combat, the attacker and defender select an "Encounter" card, which is either a numbered Attack card, or a Compromise/Negotiation card. If both cards are Attack cards, the total of the attack value and number of allied ships are added for both sides, and the side with the larger value wins with the defending player winning in case of ties. If the attacking side wins, the defender's base is lost and all ships and allies' ships are sent to the Warp, while the attacker and their allies gain the base on that planet. If the defending side wins, the attacker and allies' ships are sent to the Warp, and defending allies gain a bonus of either a ship from the warp or a new card for each ship risked. If one side plays a Compromise card against a numbered card, they immediately lose, but they, though not their allies, get "compensation" from the victor such as by drawing cards from the victor's hand. If both players use Compromise cards, they have one minute to make a deal, such as exchanging bases, while all allies are sent back to their respective bases. If a deal can't be made, both players lose ships. The player then draws a card and play proceeds to the next player.
To aid in timing, each turn is broken down into a number of phases, and cards and powers will typically indicate which phases the game elements can be played in. In particular, the edicts/artifacts cards, which generate an immediate effect such as releasing all tokens from the Warp, may only be played during specific phases which will be listed on the card, while certain features of alien powers can only be triggered in specific phases.
The game becomes complex with the introduction of alien powers. These are typically drawn randomly at the start of the game and known to all players; however, variants exist where players can select their powers, use multiple powers simultaneously, or hide their powers until they are used. Each power gives the player a way to bend the core rules to their advantages, typically in one of the following ways:
- Continuous effects, such as the Macron where each ship is valued as 4 ships
- Combat resolution effects, such as the Void where any ship that loses against it is pulled from the game instead of going to the Warp
- Victory condition changes, such as Masochist that wins if it loses all its ships
- Role-playing elements, such as the Sniveler, where the player, if they are in the losing position, must whine to the other players to gain benefits.
A player's alien power is only active if they control three or more bases in their home system, and if lost, can be regained by taking back a third base.
More advanced optional game components can add further levels of complexity and unpredictability. No edition has all of the optional components. They include:
- Flares: Cards that grant a limited version of an alien power, or, if used by the player that possesses that power, a significant advantageous gain.
- Lucre: In-game currency that allows more control of resources (such as buying more cards for one's hand). Multiple alien powers affect Lucre.
- Moons: Colonies on moons do not count towards victory conditions, but occupying one grants access to its special ability. Moon abilities can be powerful (such as retaining an alien power when it would normally be lost), while others are best described as "silly" (such as forcing the owner to speak in rhyme).
- Special planetary systems: Printed on the reverse side of the normal systems in most prints of Cosmic Encounter, the special systems have additional rules in regards to the player's initial setup, colonies, and victory conditions.
- Technologies: An array of boosts and special abilities, none of which can be used right away. Technology cards are placed face down on the table. The owner may move one ship from a planet onto the card at the start of any player's turn. Once the number of ships on the card meets the card's cost, technology is "discovered," the ships return, and the card is flipped face up. The power of technology cards varies wildly. The Xenon lasers card costs two ships, and its owner may change encounter scores by one point. The Omega missile card costs eight ships, and destroys a planet.
- Rewards: A deck's worth of incentives, reward cards can only be drawn by victorious defensive allies. Reward cards include "kickers," multipliers for encounter cards, and "rifts," booby traps that free ships from the warp, or send ships there if they ever change hands.
Some players have created their own "homemade" powers, and have posted these along with other various game extensions on the Internet.
Major variants include multiple-power games (in which players have multiple alien powers at once) and hidden-power games (in which powers are not revealed until their first use). Official variants include rules for adding a seventh or eighth player, and there has been a version providing enough components for a ten-player game (when combined with a previous release).
The original version of Cosmic Encounter had exactly six alien powers and was designed for up to six players. This edition was nearly published by Parker Brothers in the mid-1970s; when it was not, the designers founded Eon Games to publish it.
The first Eon edition was released in 1977. It allowed up to four players and included fifteen alien powers. Over the next five years, Eon released nine expansions, adding sixty more alien powers, components for a fifth and sixth player, and several new types of pieces, including "Flare" cards, money (Lucre), Moons, and special power planet systems. The artwork on these early editions included images painted by Dean Morrissey.
In 1986, the game was republished in the U.S. by West End Games. The game used the same deck of cards and number of players, and the same powers with five additional powers from Eon expansion sets #1 and #2. However, the cards and tokens were incompatible with the Eon edition. Meanwhile, in the UK, the game was published by Games Workshop. The GW edition supported six players, with powers from the Eon base set and some of the first three expansions.
In 1991, the game was licensed by Mayfair Games. Mayfair published Cosmic Encounter, an expansion called More Cosmic Encounter (1992), and a stripped-down introductory version of the game called Simply Cosmic (1995). The Mayfair edition revised some powers from the original Eon set, introduced many more, and significantly revised some of the existing components. It also introduced several new components. By combining the three Mayfair products, it is possible to play a 10-player game.
On August 17, 2007, Fantasy Flight Games announced plans to reprint the game in 2008.  Game designer Kevin Wilson gave demonstrations of the Fantasy Flight Cosmic Encounter version at Gen Con 2008, and the game was released in December. This edition included 50 aliens, flare cards, a new Technology variant, and support for 5 players. Since 2008, Fantasy Flight has released five expansion sets:
- Cosmic Incursion (released February 2010) added 20 aliens, flare cards, support for a sixth player (planets, orange ships, and destiny cards), and a "Rewards" deck which includes, among other things, Kickers and Rifts.
- Cosmic Conflict (released February 2011) added 20 new aliens, flare cards, black ships and planets to support an additional player, and a "Hazard" deck which adds special conditions to encounters.
- Cosmic Alliance (released March 2012) added 20 new aliens, flare cards, support for an eighth (white) player, and rules for team play.
- Cosmic Storm (released August 2013) added 25 new aliens, flare cards, and 10 space station cards (but no support for an extra player).
- Cosmic Dominion (released August 2014) added 30 new alien races, flare cards, a rewards deck, and ship markers that allow for suggested variants (but no support for an extra player). 
In 2003, original designer Peter Olotka and partners launched a new version called Cosmic Encounter Online that may be played over the internet. As of 2010[update], this version has 35 powers, including four new aliens and two more that are designed for online play (such as Dork, which blocks other players' screens).
Bruno Faidutti comments: "The box for Eon's first edition of Cosmic Encounter proclaimed 'the science-fiction game with everything.' And, indeed, long before today's collectible card games, live-action roleplaying games, and massively multi-player online RPGs, Cosmic Encounter was the game with everything."
The possibility of an organic and completely different experience every time one plays was one of the influences in the design of the card game Magic: The Gathering. Magic designer Richard Garfield has often cited Cosmic Encounter as being influential in the design of Magic, the Gathering, going so far as to say, "[Magic's] most influential ancestor is a game for which I have no end of respect: Cosmic Encounter."
- "Origins Award Winners (1991)". Academy of Adventure Gaming Arts & Design. Archived from the original on 2008-03-15. Retrieved 2007-11-02.
- "Origins Award Winners (1996)". Academy of Adventure Gaming Arts & Design. Archived from the original on 2007-12-21. Retrieved 2007-11-02.
- "Fantasy Flight Games to republish classic Eon games". Fantasy Flight Games. Retrieved 2008-05-15.
- "Cosmic Encounter, coming in November". Boardgame News. Retrieved 2008-08-02.
- Faidutti, Bruno (2007). "Cosmic Encounter". In Lowder, James. Hobby Games: The 100 Best. Green Ronin Publishing. pp. 66–68. ISBN 978-1-932442-96-0.
- Game design workshop: a playcentric approach to creating innovative games
- W. Eric Martin. "Peter Olotka on Cosmic Encounter and D*ne". Boardgame news.
We stole heavily from Cosmic Encounter when we designed Dune; the idea of having these well-defined and different powers, we applied it to Darkover, to Dune, and to Cosmic Encounter.
- Hemmings, Fred (June–July 1978). "Open Box: Comic Encounter". White Dwarf (Games Workshop) (7): 18. ISSN 0265-8712.
- Cosmic Encounter's Facebook  page
- Cosmic Encounter Online Cosmic Encounter Online
- Fantasy Flight Games' Cosmic Encounter page
- Cosmic Encounter Library showing the complete version history along with photos and components as well as general CE information.
- TheDiceTower.com Interview with game designer Peter Olotka, June 13, 2005
- GameSpy.com Interview with game designer Peter Olotka, January 2002
- Cosmic Encounter at BoardGameGeek