The Lone Star Series is a Major League Baseball (MLB) rivalry featuring Texas' two major league franchises, the Houston Astros and Texas Rangers. 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 (AL) and the Astros were a member of the National League (NL) until 2012. During interleague play, the winner of the six-game series was awarded the Silver Boot, a 30-inch (760 mm) tall display of a size 15 cowboy boot cast in silver, complete with a custom, handmade spur. If each team had won three games each for a tie, the declared winner was the team that scored the most runs over the course of the series. In 2013, the Astros joined the American League West with the Rangers and changed their rivalry from an interleague to an intradivision contest. The rivalry, which was once dormant, has become far more heated in recent seasons. From 2013 to 2022, 19 games were played each season. Beginning in 2023, the teams play each other 13 times a year.

The Houston Astros are an American professional baseball team based in Houston. The Astros compete in Major League Baseball (MLB) as a member club of the American League (AL) West Division, having moved to the division in 2013 after spending their first 51 seasons in the National League (NL). They are one of two major league clubs based in Texas; the Texas Rangers belong to the same division.