The Montreal Expos (French: Les Expos de Montréal) were a Canadian professional baseball team based in Montreal, Quebec. The Expos were the first Major League Baseball (MLB) franchise located outside the United States. They played in the National League (NL) East division from 1969 until 2004. Following the 2004 season, the franchise relocated to Washington, D.C., and became the Washington Nationals.

Immediately after the minor league Triple-A Montreal Royals folded in 1960, political leaders in Montreal sought an MLB franchise, and when the National League evaluated expansion candidates for the 1969 season, it awarded a team to Montreal. Named after the Expo 67 World's Fair, the Expos originally played at Jarry Park Stadium before moving to Olympic Stadium in 1977. The Expos failed to post a winning record in any of their first ten seasons. The team won its only division title in the strike-shortened 1981 season, but lost the 1981 National League Championship Series (NLCS) to the Los Angeles Dodgers. The team was sold in 1991 by its majority, founding owner, Charles Bronfman, to a consortium headed by Claude Brochu. Felipe Alou was promoted to the team's field manager in 1992, becoming MLB's first Dominican-born manager. He led the team to four winning seasons, including 1994, where the Expos had the best record in baseball before a players' strike ended the season. Alou became the Expos leader in games managed (1,409).

The aftermath of the 1994 strike initiated a downward spiral as the Expos chose to sell off their best players, and attendance and interest in the team declined. Following a failed attempt to disband the Expos, Major League Baseball purchased the team prior to the 2002 season after the club failed to secure funding for a new ballpark. In their final two seasons, the team played 22 home games each year at Hiram Bithorn Stadium in San Juan, Puerto Rico. On September 29, 2004, MLB announced the franchise would relocate to Washington, D.C. for the 2005 season, and the Expos played their final home game in Montreal.

The Expos posted an all-time record of 2,753 wins, 2,943 losses and 4 ties during their 36 years in Montreal. Vladimir Guerrero led the franchise in both home runs and batting average, and Steve Rogers in wins and strikeouts. Three pitchers threw four no-hitters: Bill Stoneman (twice), Charlie Lea, and Dennis Martínez, who pitched the 13th official perfect game in Major League Baseball history. The Expos retired four numbers in Montreal, and nine former members have been elected to the National Baseball Hall of Fame, with Gary Carter, Andre Dawson and Tim Raines' plaques depicting them with Expos caps.