The son of a rabbi, Segal attended Midwood High School in Brooklyn and traveled to Switzerland to take summer courses. He attended Harvard College, graduating as both the class poet and Latin salutatorian in 1958, after which he obtained his master's degree (in 1959) and a doctorate (in 1965) in comparative literature, from Harvard University.

Segal was a professor of Greek and Latin literature at Harvard University, Yale University and Princeton University. He had been a supernumerary fellow and subsequently an honorary fellow of Wolfson College, Oxford.

Yellow Submarine

In 1967, from the story by Lee Minoff, he wrote the screenplay for The Beatles' 1968 motion picture, Yellow Submarine.

Love Story

In the late 1960s, Segal collaborated on other screenplays, and also had written a synthetic romantic story by himself about a Harvard student and a Radcliffe student, but failed to sell it. However, literary agent Lois Wallace at the William Morris Agency suggested he turn the script into a novel and the result was a literary and motion picture phenomenon called Love Story. A New York Times No. 1 bestseller, the book became the top selling work of fiction for 1970 in the United States, and was translated into 33 languages worldwide. The motion picture of the same name was the number one box office attraction of 1970.

Segal went on to write more novels and screenplays, including the 1977 sequel to Love Story, called Oliver's Story.

He published a number of scholarly works as well as teaching at the university level. He acted as a visiting professor for the University of Munich, Princeton University, and Dartmouth College. He wrote widely on Greek and Latin literature. His novel The Class (1985), a saga based on the Harvard Class of 1958, was also a bestseller, and won literary honour in France and Italy. Doctors was another New York Times bestseller from Segal.

Segal was married to Karen James from 1975; they had two daughters, Miranda and Francesca Segal. Francesca, born in 1980, is a freelance journalist and literary critic and currently The Observer's Debut Fiction columnist.

Segal, who suffered from Parkinson's disease, died from a heart attack on January 17, 2010, and was buried in London. In a eulogy delivered at his funeral, his daughter Francesca said, "That he fought to breathe, fought to live, every second of the last 30 years of illness with such mind-blowing obduracy, is a testament to the core of who he was -- a blind obsessionality that saw him pursue his teaching, his writing, his running and my mother, with just the same tenacity. He was the most dogged man any of us will ever know."