This is a list of seasons completed by the Washington Nationals, originally known as the Montreal Expos, professional baseball franchise; they have played in the National League from their inception in 1969. They are an American professional baseball team that has been based in Washington, D.C. since 2005. The Nationals are a member of both the Major League Baseball's (MLB) National League Eastern Division. Since the 2008 season, the Nationals have played in Nationals Park; from 2005 through 2007, the team played in Robert F. Kennedy Memorial Stadium.
The Nationals are the successors to the Montreal Expos, who played in Montreal, Quebec, Canada, from their inception as an expansion team in 1969 through 2004, with the majority of that time (1977–2004) spent in Montreal's Olympic Stadium.
The following takes into account both teams, as all Montreal records were carried with the franchise when it moved to Washington.