The "Curse of the Bambino" was a superstition attributed to the sale of American baseball legend Babe Ruth from the Boston Red Sox to the New York Yankees in 1919. The sale, the story goes, relegated the Red Sox, one of the winningest baseball franchises in the early part of the 20th Century, to also-rans for decades to come and elevated the Yankees, previously not so successful, into a dynasty that has won 27 World Series championships. Frazee announced the deal on December 26, 1919, and the deal was completed on January 3, 1920.

The Red Sox won the very first World Series, in 1903 (as the Boston Americans) and then won again in 1912, 1915, 1916, and 1918. Ruth had joined the team in 1914 and emerged as one of the top pitchers in baseball. He led the league in 1916 and, in that year's World Series, pitched every bit of a 14-inning victory over the Chicago Cubs (in Game 3). He won two games in the 1918 World Series.

As the story goes, Red Sox owner Harry Frazee was looking for money to finance a Broadway musical and a found a willing buyer in the Yankees, who parted with $125,000 in order to get Ruth, known as the "Bambino." The story also goes that this particular musical was No, No Nanette, which didn't see the light of day until five years later, by which time Frazee had sold off the Red Sox as well and the Yankees were already appearing in the World Series. (They won the American League pennant three straight years beginning in 1921 and won the World Series in 1923.)

The reality is that Frazee had close to the Yankees and that he was in the habit of selling them players in order to finance his other business deals, including plays and musicals on Broadway. Other famous players that Frazee sold to the Yankees include Waite Hoyt and Herb Pennock, who won seven and five World Series, respectively. The other fact is that Ruth had demanded a giant salary increase, which Frazee was not prepared to pay.

After Ruth went from the Red Sox to the Yankees, the two teams' fortunes diverged markedly. The Red Sox didn't win the American League again until 1946 and didn't win the World Series again until 2004. The Yankees, meanwhile, won the American League pennants 40 times and the World Series 27 times. Ruth went on to become one of the game's icons and legends, setting all kinds of records, including the all-time home run record of 714, which was broken by Hank Aaron only decades later.

In the intervening years, the Red Sox were many times expected to win their league or the World Series but were thwarted by unlikely events. Frustrated fans found an easy target in the "Curse of the Bambino."

Some fans went to extraordinary measures to try to break the curse, including placing a Red Sox on top of Mount Everest and hiring professional exorcists to "purify" Fenway Park. The slogan "Reverse the Curse" found fame and fortune in the latter part of the 20th Century. When the Red Sox won the World Series in 2004 and then repeated as baseball's champions four years later, the "Curse" was considered reversed, especially since the 2004 Red Sox created some unlikely events of their own by coming back from a 3-0 deficit to defeat the Yankees in the American League Championship Series and then sweeping the favored St. Louis Cardinals in the World Series.