Phyllis Marguerite Grosskurth OC OOnt (née Langstaff; March 16, 1924 – August 2, 2015) was a Canadian academic, writer, and literary critic.

Grosskurth was born in Toronto, Ontario, the granddaughter of physician James Miles Langstaff.

This was followed by a controversial exploration of Freud and his inner circle; then a study of Melanie Klein, which was the source of a successful stage play called Mrs Klein written by Nicholas Wright.

Her biography of Lord Byron, The Flawed Angel, was the first comprehensive study of the subject for a generation.

Phyllis Grosskurth was in later life professor emerita at the University of Toronto, and in 2000 was made an Officer of the Order of Canada.