Ryan O'Byrne was born July 19, 1984 in Victoria, British Columbia. The third round, 79th overall selection in the 2003 NHL Entry Draft, O'Byrne is a graduate of Cornell University.
A physical defenseman, O'Byrne spent three seasons at Cornell University where season by season, he continually improved statically and was used regularly on the power play. He elected to skip his senior season and in the off-season sign a contract with the Montreal Canadiens. The following season, O'Byrne made his professional hockey debut with the AHL affiliate team for the Canadiens in Hamilton. After a full season in the AHL, O'Byrne appeared in 33 regular season games for the Canadiens and 22 games with the Hamilton Bulldogs.
On November 11, 2010, O'Byrne was shipped to the Colorado Avalanche in exchange for prospect Michael Bournival.
O'Byrne would spend the next two seasons with the Avalanche, establilshing himself as a solid, stay-at-home defender. His rugged play made him a favourite among teammates and fans.
On April 3, 2013, the NHL traded deadline, O'Byrne was traded to the Toronto Maple Leafs in exchange for a draft pick.