Omaha hold 'em (also known as Omaha holdem or simply Omaha) is a community card poker game similar to Texas hold 'em, where each player is dealt four cards and must make their best hand using exactly two of them, plus exactly three of the five community cards. The exact origin of the game is unknown, but casino executive Robert Turner first brought Omaha into a casino setting when he introduced the game to Bill Boyd, who offered it as a game at the Las Vegas Golden Nugget Casino (calling it "Nugget Hold'em"). Omaha uses a 52-card French deck. Omaha hold 'em 8-or-better is the "O" game featured in H.O.R.S.E.

Omaha hold 'em derives its name from two types of games.

"Hold'em" refers to a game using community cards that are shared by all players. This is opposed to draw games, where each player's hand is composed only of concealed cards, and stud games, where each player's unique hand contains a mix of cards visible to the other players and concealed hole cards.

In the original Omaha poker game, players were only dealt two hole cards and had to use both to make a hand combined with community cards. This version of Omaha is defined in the glossary of Super/System (under Omaha) as being interchangeable with "Tight hold 'em". Across all the variations of the game, the requirement of using exactly two hole cards is the only consistent rule. The "Omaha" part of the name represents this aspect of the game.

In North American casinos, the term "Omaha" can refer to several poker games. The original game is also commonly known as "Omaha high". A high-low split version called "Omaha Hi-Lo", or sometimes "Omaha eight-or-better" or "Omaha/8", is also played. In Europe, "Omaha" still typically refers to the high version of the game, usually played pot-limit. Pot-limit Omaha is often abbreviated as "PLO." Pot-limit and no-limit Omaha eight-or-better can be found in some casinos and online, though no-limit is rarer.^{[failed verification]}

It is often said that Omaha is a game of "the nuts", i.e. the best possible high or low hand, because it frequently takes "the nuts" to win a showdown. It is also a game where between the cards in their hand and the community cards a player may have drawing possibilities to multiple different types of holdings. For example, a player may have both a draw to a flush and a full house using different combinations of cards. At times, even seasoned players may need additional time to figure what draws are possible for their hand.

The basic differences between Omaha and Texas hold 'em are these: first, each player is dealt four hole cards instead of two. The betting rounds and layout of community cards are identical. At showdown, each player's hand is the best five-card hand made from exactly three of the five cards on the board, plus exactly two of the player's own cards. Unlike Texas hold 'em, a player cannot play four or five of the cards on the board with fewer than two of their own (nor can a player play three or four of their hole cards, which do not exist in Texas Hold 'em).

A maximum of eleven players can be dealt a hand in Omaha, regardless of whether or not burn cards are used, however Omaha is most commonly played six handed or nine handed.