1970 Major League Baseball season

The 1970 major league baseball season began on April 6, 1970, while the regular season ended on October 1. The postseason began on October 3. The 67th World Series began with Game 1 on October 10 and ended with Game 5 on October 15, with the Baltimore Orioles of the American League defeating the Cincinnati Reds of the National League, four games to one, capturing their second championship in franchise history, since their previous in 1966. Going into the season, the defending World Series champions were the New York Mets from the 1969 season.

The 41st Major League Baseball All-Star Game, was held on July 14 at Riverfront Stadium in Cincinnati, Ohio, home of the Cincinnati Reds. The National League won in twelve innings, 5–4, concluding their eight-season win streak.

During spring training, the Seattle Pilots moved to Milwaukee, Wisconsin as the Milwaukee Brewers, being the ninth team since 1953 to relocate, and the fifth of American League teams since them. Due to stadium issues and the team declaring bankruptcy, the team was sold to a Milwaukee-based group and promptly relocated. After having a team for only a single season, Seattle would be without a major league team for seven seasons until the expansion in 1977, with the enfranchisement of the Seattle Mariners. The team was tied with the coincidentally named 1901 Milwaukee Brewers (modern-day Baltimore Orioles) as the shortest-tenured team of the American League.

National League umpires began wearing numbers on the sleeves of their blazers and the new short-sleeved light blue shirts they began wearing (to replace the long sleeved shirts of previous years). The numbers were in alphabetical order (Al Barlick wore #1, Ken Burkhart #2, etc.) and this remained the annual numbering system until the 1979 season when the numbers became permanent regardless of retirements/resignations/firings/etc.