The Geordie presenter, currently in Australia for the new series of the reality show, is expected to marry next year.
Talking about their relationship previously, Donnelly admitted it was “a little strange” when the couple first got together because they had been work colleagues for so long, but said: “It’s going good. Everything’s hunky-dory.”
He was best man at the 2006 wedding of his on-screen partner Ant McPartlin, who is expected to return the favour.
Donnelly, who first found fame with McPartlin in teenage drama Byker Grove, has previously dated actress Clare Buckfield and TV presenter Georgie Thompson.
The new series of the hit ITV show starts this weekend, with veteran broadcaster Michael Buerk heading into the jungle as one of 10 contestants including former Premier League footballer Jimmy Bullard and TV presenter Melanie Sykes.