A cardroom (also spelled card room) is a gambling establishment that exclusively offers card games for play by the public. The term poker room is generally synonymous, since the gambling games played in such establishments are typically, and sometimes exclusively, variations of poker such as Texas hold 'em.

Such rooms typically do not offer slot machines or video poker, or other table games such as craps as found in casinos. However, a casino will often use the term "cardroom" or "poker room" (usually the latter) to refer to a separate room that offers card games where players typically compete against each other, instead of against "the house." In the United States, stand-alone cardrooms are typically the result of local or state laws and regulations, which often prohibit full-fledged casino gambling. This was typically the case in California until the advent of casino gambling offered by American Indian tribes in the 1990s, though card rooms continue to flourish and even expand there.

Since games played in card rooms are usually player-against-player instead of player-against-house, card room operators typically derive their revenues in one of two ways. In most, the dealer of each game (employed by the establishment) will collect a rake, a portion of the pot from each hand. At other times, a charge will be levied against each player for a specific time period, typically each half hour.

Though traditional poker variants such as Texas hold 'em, Omaha hold 'em and seven-card stud are by far the most popular games offered by card rooms (and sometimes the only games), others may offer games such as panguingue, pai gow, Chinese poker, and variations on blackjack. These so-called "California games", or "Asian games", may resemble such traditional casino games as blackjack, baccarat and even craps, but have rules that comply with various state restrictions.

Most of stand-alone card rooms are located in California, with more than a hundred such clubs licensed in 2006. Some are modest establishments with just a few tables, while others are the largest poker rooms in the world, offering as much as five times as many tables as the largest Las Vegas cardroom. Some even call themselves "casinos," even though their lack of electronic and table games would normally disqualify the use of such a term by modern standards. Hollywood Park Racetrack, a Thoroughbred race track in Inglewood, California, has an elaborate card room on its premises. Other large cardrooms are Bay 101 and Garden City in San Jose, the Commerce Casino in Commerce and the Bicycle Casino in Bell Gardens. All these clubs host major poker tournaments, which attract the game's top players and television coverage.

Poker rooms are sometimes operated illegally. New York City has been home to underground card rooms, some of which were the basis of the movie Rounders. Two rooms with more than ten tables -- the 14th Street Playstation and the 72nd Street Players Club -- were closed down by the police in 2005, but other smaller clubs continue to exist.