Baseball has been a popular sport in Japan for over a century since its introduction in 1872. It is called 野球 (やきゅう; yakyū) in Japanese, combining the characters for field and ball.

It is played at all age levels but most widely in junior high schools and senior high schools. Two tournaments are held in March and August for senior high school teams that win a prefectural tournament. The location of the tournaments is Koshien Stadium.

The highest level of competition is the professional league, started in 1920. It is called Puro Yakyū (プロ野球), meaning Professional Baseball.

Players from the Japanese leagues who have gone on to success in Major League Baseball in the United States include Hideo Nomo, Kazuhiro Sasaki, Ichiro Suzuki, Tadahito Iguchi and Hideki Matsui.

Japanese professional baseball consists of two leagues, the Central League and the Pacific League. There are also two secondary-level professional minor leagues, the Eastern League and the Western League, that play shorter schedules.

The professional season starts in late March or early April and ends in October with two or three all star games in July. In recent decades, the two leagues each scheduled 130, 135 or 140 regular season games with the best teams from each league going on to play in the "Nihon Series" or Japan Series. Prior to 1950 there was just one league, called the Japanese Baseball League. From 1973 to 1982, the Pacific League employed a split season with the first half winner playing against the second half winner in a mini-playoff to determine its champion. Then in 2004, the Pacific League played five fewer games than the Central League teams during the regular season and used a new playoff format to determine its champion. The teams in third and second place played in a best two of three series (all at the second place team's home ground) with the winner of that series going on to play the first place team in a best 3 of 5 format at its home ground. In the end, the Seibu Lions finished in second place, defeated Nippon Ham 2 games to 1, went on to take 3 of 5 games in Fukuoka against the Daiei Hawks and then defeated the Chunichi Dragons in the Japan Series, 4 games to 3, capping off their grueling playoff drive with a well-earned championship.

Beginning in 2005, the two leagues will have interleague play with each team playing two 3-game series (one home, one away) against each of the six teams in the other league. All interleague play games will be completed in a 7-week span.

Play in the Pacific League is similar to that of American League baseball, with the use of designated hitters, unlike the Central League. Unlike North American baseball, however, Japanese baseball games may end in a tie. If the score is tied after 9 innings of play, up to 3 additional innings will be played. If there is no leader after 12 innings, the game is declared a draw. Other differences from its American counterpart is that the general play is less aggressive, there are fewer home runs, the strike zone is larger near the batter but smaller away from the batter, and the ball is slightly smaller and wound tighter.

Unlike American pro teams, Japanese professional baseball teams are usually named after their corporate owners/sponsors rather than the cities that they play in.