O’Donnell, 26, will arrive at the club from New Zealand side Northland, where the forward has been plying his trade in the National Provincial Championship.
The six-foot, 260-pound prop began his professional career with Connacht in 2014, spending five years with his home provincial side as he progressed from an academy athlete to a senior team regular. O’Donnell’s time with the Galway-based outfit was highlighted by helping Connacht earn its first Pro12 title in 2016, which he won alongside then-teammate and fellow Arrows newcomer Shane O’Leary.
Upon the completion of the 2019 Pro14 season, O’Donnell left Ireland to join Japanese side Sunwolves for the remainder of the 2019 Super Rugby campaign. After impressing over his five-match stint for the Tokyo-based team, the prop received an offer to join New Zealand club Counties Manukau for the 2019 Mitre 10 Cup season.
O’Donnell got another taste of Super Rugby the following year, first suiting up for Crusaders in a 2020 preseason friendly before swapping Christchurch for Dunedin and joining Highlanders on an eight-week contract as injury cover.
The Sligo native returned to Counties Manukau for the 2020 Mitre 10 Cup season, and would remain in New Zealand for two more NPC stints, first with Canterbury in 2021, and more recently with Northland this past season.
O’Donnell has represented his country at the age-grade level, featuring at both the 2015 and 2016 Six Nations Under-20 Championships, as well as at the 2015 World Rugby Under-20 Championship.
Prior to starting his professional career, he played his grassroots rugby with his home All-Ireland League club side Sligo, as well as school side Summerhill College.