Korean KBO

The first game was played on March 27, 1982, between the Samsung Lions and the MBC Chungyong at Dongdaemun Baseball Stadium, Seoul. Then-president Chun Doo-hwan threw out the ceremonial first pitch.

The 1982 charter teams of its first season were:

• Haitai Tigers, based in Gwangju
• Lotte Giants, based in Busan
• MBC Chungyong, based in Seoul
• OB Bears, based in Daejeon
• Sammi Superstars, based in Incheon
• Samsung Lions, based in Daegu

The first Korean Series featured the Bears versus the Lions, with OB winning the championship 4-games-to-1, with a tie.

The Haitai Tigers dominated the 1980s, winning the Korean Series five times — in 1983, 1986, and 1987 through 1989. They were led by pitcher Sun Dong-yol and infielders Kim Seong-han and Han Dae-hwa. Other KBO stars whose careers took off in the 1980s were sluggers Chang Jong-hoon and Lee Man-soo.

From 1982 to 1988, the regular season was divided into two (a spring season and a fall season), with a first-half pennant winner and a latter-half pennant winner. The two pennant winners then played each other for the Korean Series championship. The 1982 campaign featured an 80-game (in total) season, which expanded to 100 games from 1983 to 1984. Rosters for each team were small (sometimes as few as 14 players), and many players in the league both pitched and batted. Bang Soo-won of the Haitai Tigers pitched the first no-hitter in Korean professional baseball history, in 1984 against the Sammi Superstars.

Mid-season 1985, the Sammi Superstars were sold and became known as the Chungbo Pintos, and the full season expanded to 110 games. Because the Samsung Lions won both half-season pennants (with a still single-season record .706 winning percentage), the Lions won the title outright so no Korean Series was played that year.

Because of the lack of a postseason in 1985, the next year saw some major changes, with the adoption of a playoff system, in which the top two teams from each half-season played for the right to get to the Korean Series. 1986 also saw the OB Bears moving from Daejeon to share Jamsil Baseball Stadium with MBC Chungyong in Seoul. A new franchise, the Binggrae Eagles, joined the league, replacing the vacancy in Daejeon made by OB's move, and expanding the league to seven teams. From 1986 to 1988, the regular season shrank to a total of 108 games.

1988 saw the Cheongbo Pintos change ownership again, becoming the Pacific Dolphins. In 1989 the KBO eliminated the two half-season pennants, moving to a single season of 120 games.

In the 1990s the Tigers were again dominant, winning the championship four times in the decade — 1991, 1993, 1996, and 1997. The Tigers were led by hitting-machine Lee Jong-beom and slugger Lee Ho-joon. Other KBO players who starred in the 1990s were Eagles' pitcher Song Jin-woo, who eventually became the all-time KBO leader in wins, strikeouts, and innings pitched; slugging catcher Park Kyung-oan, the first catcher in KBO history to hit 300 home runs; and stolen base king Jeon Jun-ho. But probably the most notable hitters to emerge from the 1990s were the Lions' Lee Seung-yuop and Yang Joon-hyuk, who between them now hold most of the KBO's career offensive records.

In 1990, MBC Chungyong became the LG Twins and an eighth franchise was added, the Ssangbangwool Raiders, who represented the North Jeolla Province region.

From 1991 to 1998, the season increased to 126 games. The Lotte Giants won the Korean Series championship in 1992; the team has not won it since. There was little other change during this period except for a few major sponsors: in 1993 the Binggrae Eagles became the Hanwha Eagles, in 1996 the Pacific Dolphins became the Hyundai Unicorns, and in 1999 the OB Bears became the Doosan Bears.

The 1998 Korean Series was won by the Hyundai Unicorns for the franchise's first championship in 16 years of existence. (The team would go on to win the championship in 2000, 2003, and 2004.)

In 1999 the season was expanded to 132 games, and the KBO separated into two divisions — the Dream League and the Magic League. The 1999 Dream League consisted of the Doosan Bears, the Lotte Giants, the Haitai Tigers, and the Hyundai Unicorns; the 1999 Magic League consisted of the Hanwha Eagles, the LG Twins, the Samsung Lions, and the Ssangbangwool Raiders. That year the Eagles — in their 14th season — won their franchise's first (and only) Korean Series championship, after 14 years in the KBO.

Bigger changes were made in 2000 when the Hyundai Unicorns moved from Incheon to Suwon, and a new franchise, the SK Wyverns, took their place in Incheon. The Ssangbangwool Raiders became defunct. The league's two-division structure slightly shifted as well, with SK taking Ssangbangwool's place in the Magic Division, and Lotte and Samsung switching divisions. Thus, the 2000 Dream League was composed of Doosan, Haitai, Hyundai, and Samsung; while the 2000 Magic League was composed of Hanwha, LG, Lotte, and SK.

Parity ruled the 2000s, with the Unicorns and Lions each winning three titles, and the upstart Wyverns winning two. The hard-luck Doosan Bears appeared in the Korean Series five times in the decade but only won it once, in 2001. Stars who emerged in the 2000s include all-time KBO hit king Park Yong-taik, the Giants' first-baseman Dae-ho Lee, and the Eagles' first-baseman Kim Tae-kyun. Other notable players from the era include slugging third-basemen Lee Bum-ho and Choi Jeong, the Bears' designated hitter Hong Sung-heon, and the Twins' long-time outfielder Lee Byung-kyu.

In 2001, the KBO returned to a single-division format. The Haitai Tigers became the Kia Tigers. From 2000 to 2012, the length of the regular season fluctuated between 126 and 133 games.

Despite its string of championships in the early 2000s, the Hyundai Unicorns franchise was disbanded in 2008. It was re-founded as the Woori Heroes and moved to Mok-dong in Seoul. In 2010, the team's naming rights were sold to Nexen Tire and the team was renamed the Nexen Heroes until the end of the 2018 season, when its naming rights were sold to Kiwoom Securities.

The Samsung Lions were a powerful team in the 2010s, winning the championship four times during six straight appearances in the Korean Series (from 2010 to 2015). The Doosan Bears were also a powerhouse, appearing in the Korean Series six times in the decade (including five straight appearances from 2015 to 2019), winning it three times.

Expansion resumed in the 2010s, with the addition of the NC Dinos, located in Changwon, which joined the league in 2013. It is the first team located in Changwon, the city having previously been the second home of the nearby Lotte Giants. The KBO played 128-game seasons in 2013–2014.

In 2015, the KT Wiz became the league's tenth franchise. They play their home games in Suwon, which had not had a team since the Hyundai Unicorns' disbandment. Since 2015 the KBO has played a 144-game season each year, and has added a fifth team to the playoffs, with the introduction of the Wild Card game. In 2015 the league also increased the active roster size of each team, from 26 to 27 (of those, 25 may play in any one game).

After a number of seasons of inflated offensive production, the KBO introduced a new "dejuiced" baseball before the 2019 season. The results showed in a significant decrease in runs per game and home runs per game.

The 2020 season was delayed by the COVID-19 pandemic, but finally started play in May 2020, with no fans in attendance. In response to the lack of live sports programming due to the pandemic, ESPN and the KBO League entered into an agreement to broadcast six games weekly for the 2020 season. The Opening Day game between the NC Dinos and Samsung Lions was broadcast as the first game under the agreement that night. Karl Ravech, Jason Benetti, Boog Sciambi, Eduardo Perez, and Jessica Mendoza, along with various guests, broadcast the game remotely via Internet from their homes. The deal was for the 2020 season only and was not renewed for 2021.