Master of Orion (abbreviated as MoO) is a turn-based, 4X science fiction strategy game in which the player leads one of ten races to dominate the galaxy through a combination of diplomacy and conquest while developing technology, exploring and colonizing star systems.

It has received several direct sequels, and additionally, a number of other games published since have been described as inspired by it, with reviewers and players divided on whether any has succeeded at recapturing the feeling and gameplay of the original.

Human and AI players control the management of colonies, technology development, ship construction, inter-species diplomacy, and combat.

[3] The software generates a map randomly at the start of each game; the player can only choose the size of the galaxy, and the number and difficulty of AI opponents.

For instance, the Humans have advantages in trade and diplomacy; the Bulrathi are the best at ground combat; the Silicoids ignore pollution and can colonize even the most hostile planets, but have slow population growth.

One planet is Orion, "throne-world of the Ancients" and most valuable research site in the galaxy,[8] protected by a powerful warship, the Guardian.

They deal more damage than any other weapon type to colonies, but cannot target ships, and always have the minimum possible range.

These traits guide their politics and economic management; for example militarists maintain large fleets and prioritize technologies which have military benefits, while ecologists put a lot of effort into pollution control and terraforming.

[22] Results depend on numbers, technology and (if one of the races involved is Bulrathi) racial ground combat bonus.

Master of Orion is a significantly expanded and refined version of the prototype/predecessor game Star Lords (not to be confused with Starlord, also released by MicroProse in 1993).

[30] Star Lords, often called Master of Orion 0 by fans,[31] was a prototype and never commercially released (its intro opens with "SimTex Software and Your Company present").

The crude but fully playable prototype was made available as freeware in 2001, stripped of all documentation and copy protection, in anticipation of the launch of Master of Orion III.

[31] Major differences between Star Lords and Master of Orion include inferior graphics and interface, simpler trade and diplomacy, undirected research, a lack of safeguards to prevent players from building more factories than are usable and the use of transports rather than colony ships to colonize new planets.

One feature of Star Lords that Master of Orion lacks is a table of relations between the computer-controlled races.

The game was eventually made available for download on FilePlanet[32] and the home page for Master of Orion III.

Emrich in a September 1993 Computer Gaming World preview described Master of Orion as "the best that galactic conquest can offer", and summarized its type of gameplay as "4X", meaning "eXplore, eXpand, eXploit, eXterminate".

The reviewer wished that the game supported multiple players, but predicted that "I think MOO will safely reign supreme well into the new year".

[44] In 1998, PC Gamer declared it the 45th-best computer game ever released, and the editors called it "a great sci-fi space epic".

[46] Master of Orion is a member of both GameSpy's Hall of Fame (2001)[47] and GameSpot's list of the greatest games of all time.

[49] In retrospective reviews, Allgame, GameSpot and IGN regarded MoO as the standard by which turn based strategy games set in space are judged.

The sequels are significantly more advanced in graphics and sound and feature large differences in gameplay, with some players claiming the original game remains the best version of the series.

[55] In 2011, a clone of MoO II, titled Starbase Orion, was published by Chimera Software, LLC for the iPhone.

The game setting has been the influence of Russian writer Sergey Lukyanenko's trilogy, the Line of Delirium.

[59] The team behind Stellaris based their game partially on the Master of Orion series,[60] but also said it was important to "try new things and leave the old formulas from the 90s behind".