The following are the baseball events of the year 1900 throughout the world.
National League final standings
- April 19 – In Boston, the Phillies win 19–17 in the NL's highest scoring opening day game. Boston tied the game with 9 runs in the ninth. Philadelphia, once up 16–4, scores 2 in the 10th for the win.
- May 5 – The Orphans' Jimmy Ryan hits his 20th career leadoff homer against the visiting Cincinnati Reds and Noodles Hahn. Chicago wins 4–3.
- June 19 - Clark Griffith and Rube Waddell have a dual for the ages. Each throw 13 shut out innings before Griffith hits a walk off double in the 14th.
- July 4 – At the West Side Grounds, about 1,000 of the 10,000 fans at the game fire pistols to celebrate July 4. No injuries were reported. Meanwhile, Chicago beats Philadelphia, 5–4, in 12 innings.
- July 7 – Kid Nichols of the Boston Beaneaters records his 300th career win.
- July 12 – Noodles Hahn pitches a no-hitter for the Cincinnati Reds against the Philadelphia Phillies. The Reds win, 4–0.
- July 13 – The Phillies' third baseman, Harry Wolverton, has 3 triples among his 5 hits in a 23–8 win over the Pirates.
- July 17 – The Giants' Christy Mathewson, acquired from Norfolk of the North Carolina League, makes his major league debut, relieving in the 5th inning against Brooklyn at Washington Park with the score tied, 5–5. The results are less than glowing: 2 walks, 3 hit batters, 5 runs. Ed Dohney relieves Mathewson after 4; the Superbas win the game, 13–7.
- August 17 - Reds pitcher Bill Phillips punches Phillies hitter Roy Thomas. This is because Thomas fouled off 12 straight pitches. Phillips is ejected but the Reds win in extras.
- January 9 – Henry Kessler, 53, shortstop who hit .253 for the Brooklyn Atlantics and Cincinnati Reds from 1873 to 1877.
- January 19 – Marty Bergen, 28, catcher for the Boston Beaneaters since 1896 who batted .280 for the 1898 championship team
- January 21 – Jim Rogers, 27, played two seasons and managed one from 1896 to 1897.
- February 7 – "Brewery Jack" Taylor, 26, pitcher for the Cincinnati Reds (among others), who had three 20-win seasons from 1894–'96, and led the National League in games and innings in the 1898 season.
- February 23 – Nate Berkenstock, 69[?], played right field for one game with the 1871 Philadelphia Athletics.
- March 31 – Foghorn Bradley, 44, pitcher for the 1876 Boston Red Caps who went on to umpire for six major league seasons.
- April 28 – Walter Plock, 30, center fielder for the 1891 Philadelphia Phillies.
- May 14 – Billy Taylor, 45[?], player for seven seasons, mostly as a pitcher and outfielder, from 1881 to 1887.
- May 15 – John Traffley, 38[?], right fielder who appeared in two games with the 1889 Louisville Colonels.
- May 31 – Tom Patterson, 55[?], outfielder for four seasons in the National Association.
- June 1 – Charlie Gray, 36[?], pitcher who went 1–4 for the 1890 Pittsburgh Alleghenys.
- June 12 – Mox McQuery, 38, first baseman who hit .271 with 13 home runs and 160 RBI in 417 games, and the National League in putouts in 1886.
- June 13 – Frank Fleet, 52[?], utility player for five seasons in the National Association.
- July 15 – Billy Barnie, 47, manager of the Orioles from 1883 to 1891, and later of three other teams; pilot of Hartford team in Eastern League since 1899.
- July 22 – Harry Jacoby, [?], infielder/outfielder for two seasons with the Baltimore Orioles of the American Association.
- July 24 – Fred Zahner, 30, backup catcher who hit .214 with the Louisville Colonels from 1894–'95.
- August 24 – John Puhl, 24, third baseman who played briefly for the New York Giants in 1898 and 1899.
- September 14 – Ed Knouff, 33, pitcher/outfielder who posted a 20–20 record and hit a .187 average in the American Association from 1885 to 1889.
- October 7 – Bill Phillips, 43, first baseman for Cleveland and Brooklyn who was the first Canadian in the major leagues; batted. 302 in 1885.
- October 9 – Harry Wheeler, 42, pitcher and outfielder for eight different teams between 1878 and 1884.
- December 14 – Jim Devlin, 34, pitcher who posted an 11–10 record with a 3.38 ERA for the New York Giants, Philadelphia Quakers and St. Louis Browns from 1886 to 1889.