Ann Louise Wagner (née Trousdale, September 13, 1962) is an American politician and former diplomat serving as the U.S. representative for Missouri's 2nd congressional district. A member of the Republican Party, she was the United States ambassador to Luxembourg from 2005 to 2009. Her district, based in St. Louis County, is heavily suburban and the state's wealthiest. It includes most of St. Louis's southern and western suburbs as well as some of the northern exurbs in St. Charles County and the northern part of Jefferson County. Before her diplomatic post, Wagner chaired the Missouri Republican Party from 1999 until 2005; she co-chaired the Republican National Committee for four years, starting in 2001. She is generally regarded as being part of the moderate bloc of her party.