Regan, 24, will leave New Zealand’s Super Rugby Aotearoa side Highlanders to join the Liberty Stadium outfit.
The former Ulster lock headed to New Zealand after he was released from his contract, joining amateur side Dunedin Sharks where he earned a place with Otago in the semi-pro Mitre 10.
He was then called up to play for the Highlanders in Super rugby.
Regan, who stands at 1.97m and weighs in at 115kg, captained Leinster at Under-18 level and was a member of Ireland’s Under-20 Six Nations and Junior World Cup squad in 2017.
Regan said: “This is a great opportunity for me with the Ospreys and a team with such a proud history.
“There was interest from other clubs, but the squad there is building impressive performances and wins and you just feel is heading for success.
“I just want to be a part of that and play my role and add some value to the squad. I cannot wait to get to Swansea and to get going.
“This a real chance to play at the top level and learn from the quality locks like Alun Wyn Jones, Adam Beard and Bradley Davies.
“I have watched a lot of the Ospreys games and you can see Toby Booth is giving young players a chance.
“For a young guy, that’s very exciting. He trusts all the young lads to do a job for the team and you cannot ask for more than that from a coach.
“This is just a great opportunity for me to develop as a player after my experiences with Ulster and the Highlanders.”
Ospreys head coach Booth said: “One of the great things about Jack is his back story.
“He has battled through adversity to get to this stage in his career. His determination and resilience are massive attributes for us to utilise going forward.”
