O'Brien is a versatile lock who can play across the back row. O'Brien has represented Ireland at U18,19 & 20 level but was ruled out of the 2014 Junior World Cup.
He broke through into the Connacht senior side in the 2015/2016 season, when he made his senior debut against Enisey-STM after replacing John Muldoon.
He made his first Pro12 appearance shortly after when he came off the bench, in a historic win, that saw Coonnacht beat Munster at Thomond Park for the first time since 1986.
O'Brien signed a contract with Connacht that will see him be a full squad member for the 2016/2017 season.
In November 2017, O'Brien signed a two-year contract extension to his contract that will see him remain at the Sportsground up to the end of 2019-20 season.
The 22-year-old Connacht native has made over 40 appearances for the province since making his senior debut in 2015.
|2015 - present|
No 5 Lock
|2014 - 2015|