The Premier12 is the flagship international tournament organised by the WBSC, featuring the 12 best-ranked national baseball teams in the world. The first tournament was held in Taiwan and Japan in November 2015 with the next scheduled to be held in 2019. 

Professional baseball is also played in domestic leagues throughout the world:

United States and Canada

Major League Baseball (MLB) in the United States and Canadian city Toronto consists of the National League and the American League.

Historically, teams in one league never played teams in the other until the World Series, in which the champions of the two leagues played against each other.

This changed in 1997 with the advent of interleague play.

In addition to the major leagues, many North American cities and towns feature minor league teams.

An organisation officially styled Minor League Baseball, formerly the National Association of Professional Baseball Leagues, oversees nearly all minor league baseball in the US and Canada.

The minor leagues are divided into classes AAA, AA, High A, Low A, Short-Season A, Advanced Rookie, and Rookie.

These minor league divisions are affiliated with major league teams and serve to develop young players and rehabilitate injured major-leaguers.

Asia

Nippon Professional Baseball (NPB), the highest level of baseball in Japan, currently consists of two six-team circuits, the Central League and the Pacific League.

Each season the winning clubs from the two leagues compete in the Japan Series, the Championship Series of NPB.

Ten teams compete in South Korea’s KBO League, which was originally founded with six franchises in 1982.

Other Asian leagues include the Chinese Professional Baseball League, the top tier of the sport in Taiwan.

Europe

The Italian Baseball League consists of eight teams, each contesting 42 games; a team plays two three-game series against every other team.

The four teams that finish with the best regular season record qualify for a round-robin playoff.

The first and second-place finishers of the round-robin are cast into the best of seven Italian Baseball Series and compete for the championship, referred to as the Scudetto.

The Honkbal Hoofdklasse is the highest level of professional baseball in The Netherlands.

It is an eight-team league that plays a 42-game schedule and is overseen by the Royal Dutch Baseball and Softball Association.

The season runs from April to September and is followed by the playoffs among the four best teams, which culminates in the Holland Series between the two winners of the playoffs. 

Croatia, France and Germany are among the other European countries to have a national baseball league.

The Caribbean

Several leagues exist in Carribbean countries, such as the Dominican Professional Baseball League (LIDOM) and the Puerto Rico Baseball League.

LIDOM is the highest level of professional baseball in the Dominican Republic, consisting of six teams.

The winter league's players include a number of prospects that go on to play in MLB in the US.

The LIDOM winners advance to play in the annual Caribbean Series, the highest baseball tournament at club level in Latin America that also features the champions of Cuba, Mexico, Puerto Rico, and Venezuela.

Central America

The Mexican Pacific League is an independent winter league with the eight-team regular season running from October to December, and a playoff series taking place in January to determine the champion.

The Mexican Baseball League is an AAA league organised in Minor League Baseball, one grade below MLB.

Unlike the other two AAA circuits, the International League and the Pacific Coast League, Mexican League teams are not affiliated with MLB teams.

Panama and Nicaragua also have professional baseball leagues with the former being played in the winter and consisting of four teams. 

The latter was re-established in 2004 having shut down in 1967 due to Nicaragua's economic difficulties. 

South America

The Colombian Professional Baseball League is a winter competition held over three months during the MLB off-season.

Venezuela also has a professional league, housing eight teams in one single division.

The tournament is divided into a regular season consisting of two rounds and a postseason consisting of two semi-final rounds and one final.

Oceania

The Australian Baseball League  is jointly funded by the Australian Baseball Federation, MLB and the Australian Federal Government. It uses the same name as a now defunct competition held during the 1990s, but is considered to be a separate competition.