Mona Ingeborg Sahlin (born 9 March 1957) is a Swedish politician who was the leader of the opposition and leader of the Swedish Social Democratic Party from 2007 to 2011.

Sahlin was a Member of Parliament, representing Stockholm County, from 1982 to 1996 and again from 2002 to 2011. She has also held various ministerial posts in the Swedish government from 1990 to 1991, from 1994 to 1995 and from 1998 to 2006. Sahlin was elected the new leader of the Social Democratic Party on 17 March 2007, succeeding Göran Persson who resigned as leader following the defeat in the 2006 general election. Sahlin is the first female leader of the Swedish Social Democratic Party and became in 2011 the first since Claes Tholin in 1907 to leave that position without having served as Prime Minister of Sweden. In 2012, her successor Håkan Juholt joined her as the second now living person to do so. On 14 November 2010, following another electoral defeat for the Social Democrats, she announced her intent to step down as party chairman, which she did in early 2011.