The 1964 Major League Baseball season was played from April 13 to October 15, 1964. This season is often remembered for the end of the New York Yankees' third dynasty, as they won their 29th American League Championship in 44 seasons. However, the Yankees lost the World Series to the St. Louis Cardinals in seven games. As of 2017, the Cardinals are the only National League team to have an edge over the Yankees in series played (3–2), amongst the non-expansion teams.
August 12 – Mickey Mantle hits a home run from both sides of the plate in a 7–3 Yankees win over the Chicago White Sox. It is the tenth time in his career that he has done so and a major league record for switch-hit homers in a game.
September 27 – Johnny Callison hits three home runs, but the Phillies lose to the Milwaukee Braves 14–8. The Phils suffer the seventh loss in their 10-game losing streak, while the Reds sweep the New York Mets (4–1 and 3–1). These results knock Philadelphia out of first place, with the Reds replacing them atop the NL standings. The Phillies would never return to first place in 1964.
September 29 – The Pittsburgh Pirates blank the Reds 2–0 at Crosley Field (despite the Reds getting 11 hits off Bob Friend) to end the Reds' nine-game winning streak. Meanwhile, the St. Louis Cardinals defeat the Phillies 4–2 at Busch Stadium, the seventh win in the Cardinals' eight-game winning streak and the ninth loss in the Phillies' 10-game losing streak. The win, Ray Sadecki's 20th of the season, puts the Cardinals into a tie for first place with the Reds; St. Louis had been 11 games out of first on August 23.
October 3 – As a result of the now-concluded Phillies' 10-game losing streak, this day begins with four teams still having a mathematical shot at the NL pennant. One of them, the San Francisco Giants, is eliminated with a 10–7 loss to the Chicago Cubs. At the end of the day's play, the Reds and the Cardinals are tied for first place, with the Phillies a game back. In recent days, the NL has had to scramble to schedule various possible playoffs.
October 4 – The Phillies defeat the Reds, 10–0, in the last regular-season game for both teams unless there is a playoff; that result clinches (for the Cardinals) a tie for the NL pennant. At the end of that game, both teams are ½ game back of the Cardinals, and await the result of the Cardinals-Mets game. Then, the Cardinals, never in first place until the last week of the season, clinch their first pennant since 1946 with an 11–5 win over the Mets, who had just beaten the Cardinals twice in the two preceding days. The win by the Cardinals averts a three-way tie for the NL pennant, with the Phillies and the Reds both finishing one game back in a second-place tie.
October 16 – The day after the final game of the World Series, the managerial posts of both pennant winning teams are vacant. In the morning, Johnny Keane, manager of the victorious St. Louis Cardinals, resigns, much to the surprise of owner Gussie Busch. Hours later, New York Yankee general manager Ralph Houk fires Yogi Berra as his manager, citing Berra's lack of control over team and his inability to command respect from his players. Less than a week later, Houk replaces Berra with Keane; meanwhile, Berra reunites with Casey Stengel as a coach with the New York Mets.
December 1 – The Houston Colt .45s officially change their nickname to Astros. The change coincides with the team's impending move from Colt Stadium to the Harris County Domed Stadium, also known as the Astrodome. A change in name for the three-year-old franchise is necessitated due to a dispute with the Colt firearm company; the Astros name is chosen due to Houston being the home of NASA's Manned Spacecraft Center (later the Lyndon B. Johnson Space Center).