John Sewell CM (born December 8, 1940) is a Canadian politician and lawyer who served as the 58th mayor of Toronto from 1978 to 1980.

[2] Sewell became active in city politics in 1966 when he joined the residents of the Trefann Court Urban Renewal Area in the fight against the expropriation and levelling of the working-class and poor neighbourhood.

[3] He was first elected to Toronto City Council in 1969 as alderman for Ward 7, a predominantly working-class area including St. Jamestown, Regent Park, Don Vale, and Cabbagetown.

[6] As an environmentalist famous for riding his bicycle to council, he opposed the development of banking and convention centres in the central business district that would become the hallmark of the mayors who followed.

In the 1980 election, after two years of controversy, pro-development Conservatives and Liberals encouraged and united behind the candidacy of Art Eggleton who was presented as the establishment candidate.

Sewell served as chair of the Toronto public housing authority from 1986 to 1988 and is an acknowledged urban affairs expert.

In the 1999 Ontario provincial election, Sewell ran as an independent candidate in the riding of Toronto Centre—Rosedale, challenging Progressive Conservative cabinet minister Al Leach to protest the megacity.

Sewell was also criticized for remaining in the race after Leach, whom he had personally targeted as the minister responsible for amalgamation, had withdrawn from the contest.