The QI star, Stephen Fry 57, is said to be head over heels and smitten with comedian and writer Elliott Spencer, who he is believed to have begun dating last year.
The couple have a year to tie the knot after giving formal notice at Fry’s local register office in Dereham, Norfolk.
A pal told The Sun newspaper: “Since Stephen met Elliott it is like he has a new lust for life.”
Stephen, who has been open about suffering from loneliness and depression in the past, is said by pals to be his old self again in the company of his three decade younger lover.
The pair, who have known each other for some time, have been spotted together at London Savoy Hotel and at Ascot racecourse in Berkshire.
Since they met, they have exchanged a string of messages on social networking site Twitter.
After one meeting Elliott, 27, gushed: “I had the confidence of a gnat when I met Mr @stephenfry Show him some respect he’s the man.”