American League East

The Red Sox–Yankees rivalry

The Red Sox–Yankees rivalry is one of the oldest, most famous and fiercest rivalries in American sports. For more than 100 years, the Boston Red Sox and New York Yankees have been intense rivals.

The Red Sox–Rays rivalry

The Red Sox and the Tampa Bay Rays have a rivalry that has been the focus of memorable incidents over the years, despite the fact that, as of 2017, the Rays have existed for less than 20 years. The two teams met in the 2008 ALCS with the Rays winning the series en route to their first World Series appearance:

American League West

Lone Star Series: Texas Rangers vs Houston Astros

The Lone Star Series (also, Silver Boot Series) is a Major League Baseball rivalry featuring Texas' two major league franchises, the Texas Rangers and Houston Astros. It is an outgrowth of the "natural rivalry" established by MLB as part of interleague play as the Rangers are a member of the American League and the Astros were a member of the National League until 2012.