In the World Series, a sweep refers to a Major League Baseball (MLB) team winning four straight games and losing none in a best-of-seven format.
There have been 19 sweeps in World Series history. The American League has been responsible for thirteen of the sweeps, with the New York Yankees account for more than half of those, with a record eight. The National League is responsible for the remaining six sweeps, with the New York / San Francisco Giants and the Cincinnati Reds each achieving two.
The first sweep is credited to the 1914 "Miracle" Boston Braves who defeated the 1914 Philadelphia Athletics in four straight games. The most recent sweep occurred in the 2012 World Series, when the San Francisco Giants defeated the Detroit Tigers.
There is a dispute as to whether the following World Series can be considered sweeps as, in both cases, while the team did win four games and lost none, each series had a tied game. A number of sources do not recognize them as official sweeps while others list them as such.
The New York Yankees have completed the most numbers of sweeps in MLB history, with eight. The New York / San Francisco Giants, Cincinnati Reds, and Boston Red Sox are tied at second with two each. To date, the Red Sox are the only team with multiple sweeps to have never been swept themselves.
The most times a team has been swept is two, with four teams "earning" the distinction: Chicago Cubs, Philadelphia / Oakland Athletics, New York Yankees, St. Louis Cardinals. Of those teams, the Cubs and the Cardinals have never completed a sweep themselves.
In the 25 times teams have taken a 3-0 World Series lead, the opponent has forced a Game 5 four times. No team which has forced a World Series Game 5 has gone on to force a Game 6, let alone complete a comeback, i.e. a "reverse sweep."