Katharine Blake (born Illonne Katharine Inglestone, September 11, 1921 – March 1, 1991) was a British actress, born in South Africa, with an extensive career in television and films. She won the BAFTA for Best Actress for her work in television in 1964. She portrayed Elizabeth Boleyn in the film Anne of the Thousand Days (1969).

In 1969/1970, she played the character Chris Nourse in first an episode of Public Eye and then in Armchair Theatre's Wednesday's Child; one of the first lesbian love affairs to be seen on UK television. She replaced Googie Withers as the Prison Governor in the ITV series Within These Walls in 1977, but only appeared in one season, leaving the role due to ill health.

Her first husband was actor Anthony Jacobs (1942-1948,1 child), her second husband was actor/director David Greene (1948-1959,1 child), and her third husband was director Charles Jarrott (1959-1982). She was estranged from her 2 daughters at the time of her death.