Joan Kelly Horn (born October 18, 1936) is an American politician from Missouri. She served one term in the US House of Representatives representing the state's 2nd Congressional District in suburban St. Louis. She is a Democrat.
She was elected to Congress in 1990, upsetting incumbent Republican Jack Buechner. Earlier in 1990, the Democratic-controlled Missouri state legislature approved a new congressional district map that was intended to preserve heavy Democratic majorities in the two districts which included St. Louis itself--the 1st, represented by Democrat Bill Clay and the 3rd, represented by then-House Majority Leader Dick Gephardt. However, the new map had been drawn well before the elections, and no one had anticipated Horn's upset win over Buechner. Horn realized the new map put her in serious electoral trouble, and asked that the map be redrawn, even requesting a sliver of St. Louis. However, Gray and Gephardt turned her down. In November 1992, Horn was narrowly defeated by Republican State House Minority Leader Jim Talent. She was badly defeated in a rematch against Talent in 1996.
Preceded by: Jack Buechner United States Representative for the 2nd Congressional District of Missouri 1991-1993 Succeeded by: Jim Talent