David Hemblen was an English actor who frequently worked in Canadian film, television and theatre. He grew up in Toronto, Ontario, where he pursued a classical education before turning to theatre. He received an M.A. in English and was working towards a Ph.D. in medieval studies when he was spotted during a rehearsal of a university production by Clifford Williams of the Royal Shakespeare Company. Hemblen was offered a season at Toronto's Royal Alexandra Theatre. Hemblen's career in theatre included many productions at the Stratford Festival and four seasons at the renowned Shaw Festival in Niagara-on-the-Lake. He received a Dora Award nomination for Best Actor for his portrayal of Dr. Astrov in Toronto's Tarragon Theatre production of Uncle Vanya. He also received a Genie Award nomination as Best Actor in Family Viewing.

Hemblen's television career began in the early 1970s, and he appeared in a number of Canadian television series, including The Beachcombers, Night Heat, and Street Legal. He also had recurring roles in the American series T. and T. and The X-Files.

Hemblen's most famous role was as Johnathan Doors in the science fiction series Earth: Final Conflict. He played the role from 1994 to 2002, and his performance was critically acclaimed. He also voiced the character of Magneto in the X-Men animated series from 1992 to 1997.

Hemblen died on November 16, 2020, in Toronto, Ontario, at the age of 79. He was survived by his wife, actress Kate Nelligan, and their two daughters.