The couple are claimed by Gossip Cop to have quietly parted ways back in spring, but to have remained friends in spite of the split.
Quinto, who plays Spock in JJ Abrams' Star Trek movies, came out as gay last year.
He later said that it had not affected the amount of roles he was offered.
"I haven't stopped working, I've only worked more since I came out," he said on The Jonathan Ross Show.
Watch MTV News on the hour every hour on MTV - Sky Channel 126 and Virgin Channel 134