Margaret Mary Ritchie, Baroness Ritchie of Downpatrick (born 25 March 1958 in Downpatrick), is an Irish politician who was the Leader of the Social Democratic and Labour Party (SDLP) from 2010 to 2011. She was previously the Minister for Social Development in the Northern Ireland Executive from 2007 to 2010, when she was elected as the Member of Parliament (MP) for South Down.