John Clarkson was an American professional baseball pitcher who played in the National League and American Association from 1882 to 1894. He was known as one of the greatest pitchers of his era, and was the first pitcher in Major League Baseball history to win 300 games.

Clarkson was born in Cambridge, Massachusetts in 1861. He began his professional career in 1882 with the Worcester Ruby Legs of the National League. He quickly established himself as one of the league's best pitchers, leading the league in wins in 1883 and 1885. He also led the league in strikeouts in 1884 and 1885.

In 1886, Clarkson joined the Chicago White Stockings of the National League. He continued to be one of the league's best pitchers, leading the league in wins in 1887 and 1888. He also led the league in strikeouts in 1887 and 1889.

In 1890, Clarkson joined the Boston Beaneaters of the National League. He continued to be one of the league's best pitchers, leading the league in wins in 1891 and 1892. He also led the league in strikeouts in 1891 and 1892.

Clarkson retired from professional baseball in 1894 with a career record of 328-178 and a 2.81 ERA. He was inducted into the Baseball Hall of Fame in 1963.

John Clarkson was one of the greatest pitchers of his era. He was the first pitcher in Major League Baseball history to win 300 games, and he led the league in wins and strikeouts multiple times. He was inducted into the Baseball Hall of Fame in 1963, and his legacy as one of the greatest pitchers of all time lives on.