Stephen Henry Lewis is a Canadian politician, public speaker, broadcaster, and diplomat. He was the leader of the social democratic Ontario New Democratic Party for most of the 1970s.

The Ontario New Democratic Party is a social-democratic political party in Ontario, Canada. The party currently forms the Official Opposition in Ontario following the 2018 general election. It is a provincial section of the federal New Democratic Party. It was formed in October 1961 from the Co-operative Commonwealth Federation and the Ontario Federation of Labour (OFL).