Nicol Ross Stephen, Baron Stephen (born 23 March 1960) is a Scottish politician who served as Deputy First Minister of Scotland and Minister for Enterprise and Lifelong Learning from 2005 to 2007. A member of the Scottish Liberal Democrats, he was the Member of the Scottish Parliament (MSP) for Aberdeen South from 1999 to 2011, and was leader of the Scottish Liberal Democrats from 2005 to 2008.

Stephen was elected to the Scottish Parliament in 1999. Following the coalition agreement between the Scottish Liberal Democrats and Scottish Labour, he became Deputy Minister for Enterprise and Lifelong Learning. Later in the same parliamentary term he became Deputy Minister for Education, Europe and External Affairs, and then for Education and Young People. Following the 2003 Scottish Parliament election, he joined the Scottish Executive cabinet as Minister for Transport.

In 2005, following the resignation of his predecessor Jim Wallace, Stephen was elected leader of the party and also became deputy first minister and Minister for Enterprise and Lifelong Learning. He led his party into the 2007 election, where it won 16 seats (down one on 2003). He resigned as party leader on 2 July 2008, triggering a leadership election. In 2011 he joined the House of Lords. He became a patron of The Aberdeen Law Project in 2011.