The 1983 Major League Baseball season ended with the Baltimore Orioles defeating the Philadelphia Phillies in the fifth game of the World Series. Rick Dempsey was named MVP of the Series. The All-Star Game was held on July 6 at Comiskey Park; the American League won by a score of 13–3, with California Angels outfielder Fred Lynn being named MVP.
April 27 – Nolan Ryan strikes out Brad Mills of the Montréal Expos. It is the 3,509th strikeout of Ryan's career, breaking the long time record established by Walter Johnson. Ryan will go on to break his own record 2,205 times before retiring.
July 24 – In the game now known as the Pine Tar Game, George Brett hits an apparent go-ahead 2-run home run off Goose Gossage in the ninth inning of a game against the New York Yankees at Yankee Stadium. However, Yankees manager Billy Martin challenges that Brett's bat had more than the 18 inches (460 mm) of pine tar allowed, and home plate umpire Tim McClelland upholds Martin's challenge. After being called out and having the home run nullified, Brett goes ballistic and charges out of the dugout after McClelland. The AL president's office later upholds the Kansas City Royals protest, restoring the home run, and the game is completed on August 18, with the Royals winning 5–4.
July 29 – Steve Garvey, first baseman for the San Diego Padres dislocates his thumb, and ends his streak of 1,207 consecutive games played. It is still the National League record for consecutive games played.