Gunn, considered to have written some of the best poetry of his time, died Sunday in his sleep, said Mike Kitay, Gunn's partner of 54 years, BBC reported Thursday.
"I thought he was possibly the best living poet in English," said Wendy Lesser, an author and editor of the literary journal The Threepenny Review. "Unlike most poets, he was equally at home in rhyme and non-rhyme, in free verse and patterned rhythms."
Gunn, part of a group of British poets known as The Movement, along with Philip Larkin and Kingsley Amis, published his first book, "Fighting Terms," at age 25.
Gunn received many literary awards, including the prestigious David Cohen British Literature Prize last year.
Gunn, born in 1929 in Kent, England, moved to San Francisco in 1954. He taught at the University of California at Berkeley, Calif., from 1958 to 1966 and from 1973 to 1990.