The Astros defeated the Boston Red Sox 3–1 in the 2017 American League Division Series (ALDS). This is the Astros' fifth appearance in a League Championship Series, and their first since transferring from the National League to the American League. Their only previous LCS win came in the 2005 National League Championship Series; they lost in 1980, 1986, and 2004. They are also the first AL West team to make it to the ALCS since 2011.