The 20-year-old attacker put pen to paper following a successful trial with the Hoops, during which he bagged two goals in a friendly against Newcastle United.
Michael arrives from Derry City, having broken into the Candystripes’ first-team over the last three seasons.
Speaking to Celtic TV, the Irishman admitted that he was elated to have joined his Bhoyhood heroes.
“It feels amazing. It’s like a dream come true,” he said. “I came over here on trial just before Christmas and spent eight days here and saw two matches that I’d never been to before. It was brilliant.
“I’m now going to work hard and try my best to make an appearance for the first-team and make the fans happy. This is the club I’ve always supported and this is huge for me.”