The 2005 Major League Baseball season was notable for the league's new steroid policy in the wake of the BALCO scandal, which enforced harsher penalties than ever before for steroid use in Major League Baseball. Several players, including veteran Rafael Palmeiro, were suspended under the new policy. Besides steroids it was also notable that every team in the NL East division finished the season with at least 81 wins (at least half of the 162 games played). Additionally it was the first season featuring a baseball team in Washington, D.C. after more than 3 decades (the second iteration of the Washington Senators last played there in 1971), with the Washington Nationals having moved from Montreal.
The Anaheim Angels changed their name to the Los Angeles Angels of Anaheim.
The season ended when the Chicago White Sox defeated the Houston Astros in a four-game sweep in the World Series, winning their first championship since 1917.
As of the 2021 season, this is the last season in which no no-hit games were pitched; 2005 was also only the 6th year since 1949 in which no such games were thrown.