The 2005 National League Championship Series (NLCS), the second round of the 2005 National League playoffs, matched the Central Division champion and defending league champion St. Louis Cardinals against the wild card qualifier Houston Astros, a rematch of the 2004 NLCS. The Cardinals, by virtue of having the best record in the NL during the 2005 season, had the home-field advantage. The Astros won the series four games to two, and became the National League champions; they faced the American League champion Chicago White Sox in the 2005 World Series, where the Astros lost to the White Sox in a sweep in four games.

The 2006 National League Championship Series (NLCS), the second round of the 2006 National League playoffs, began on October 12 and ended on October 19; it was scheduled to begin on October 11, but was postponed a day because of inclement weather. The St. Louis Cardinals defeated the heavily favored New York Mets in seven games to advance to the 2006 World Series against the Detroit Tigers.