Gage and Appleton have shared plenty of photographs together in recent months - on Instagram and on red carpets - but had not admitted to the relationship until recently.
Appearing on the Today Show in the US, Gage confirmed he and Appleton were an item, adding that he was "very much in love".
“I feel very happy, very lucky and very much in love,” he told the hosts.
Gage, who was on the morning show to promote his latest appearance in Netflix series You, was also full of praise for his hunky partner.
"That is a good looking man," he said as the production rolled through photos of the couple on vacation in Europe.
"There was just something about being in London," Gage said of his time filming You.
"I got a taste of the Brits and couldn’t help myself."
During the interview, conversation turned to Appleton when Gage was asked about his hair and whether the celebrity hair stylist would approve.
"I think this mane needed to be tamed," Gage responded, adding: “I also needed to be tamed.”
Appleton has been responsible for many celebrity quaffs, including that of Kim Kardashian and Jennifer Lopez.