The Cork man spent the past season with Bedford Blues in the RFU Championship.
He has also previously played for Gloucester Rugby in the English Premiership, played AIL rugby with University College Cork and been part of the Munster Rugby Sub-Academy.
O’Connor has represented Ireland internationally at U20 level, being a part of the squad at the 2018 U20 World Rugby Championship.
On the news, O’Connor added:
“I’m delighted to sign with the province and I’m looking forward to getting integrated into the squad.
I feel I can add to the group here and can improve my game under the coaching staff. I’m excited to get going for the rest of the season.”
Ulster Rugby’s Head of Recruitment and Rugby Operations, Bryn Cunningham added:
“Bryan has had a few years playing over in England and we feel, with his physical profile, there was an opportunity to bring him in and add to our squad depth at tighthead.
Bryan joins a front row with a similar age- profile and we look forward to seeing his development and contribution over the season ahead.”