<P> The Yankees -- Red Sox rivalry is a Major League Baseball ( MLB ) rivalry between the New York Yankees and Boston Red Sox . The two teams have competed in MLB 's American League ( AL ) for over 100 seasons and have since developed one of the fiercest rivalries in American sports . In 1919 , Red Sox owner Harry Frazee sold star player Babe Ruth to the Yankees , which was followed by an 86 - year period in which the Red Sox did not win a World Series . This led to the popularization of a superstition known as the `` Curse of the Bambino '' , which was one of the most well - known aspects of the rivalry . </P>
<P> The Yankees -- Red Sox rivalry is a Major League Baseball ( MLB ) rivalry between the New York Yankees and Boston Red Sox . The two teams have competed in MLB 's American League ( AL ) for over 100 seasons and have since developed one of the fiercest rivalries in American sports . In 1919 , Red Sox owner Harry Frazee sold star player Babe Ruth to the Yankees , which was followed by an 86 - year period in which the Red Sox did not win a World Series . This led to the popularization of a superstition known as the `` Curse of the Bambino '' , which was one of the most well - known aspects of the rivalry . </P>
when did the red sox yankees rivalry began
when did the red sox yankees rivalry began
1919
1919