The award is given annually to the player "adjudged to have exhibited the best type of sportsmanship and gentlemanly conduct combined with a high standard of playing ability."
O'Reilly joins Florida's Aleksander Barkov and Calgary's Sean Monahan as finalists for the award.
The winner is selected with votes from members of the Professional Hockey Writers' Association and will be revealed at the 2019 NHL Awards on June 19.
O'Reilly previously won the Lady Byng in 2014 as a member of the Colorado Avalanche.
Pavol Demitra (2000), Brett Hull (1990) and Phil Goyette (1970) are the only players in Blues history to win the award, which was first presented in 1925. Other winners include Wayne Gretzky, Marcel Dionne, Mike Bossy, Joe Mullen, Ron Francis, Paul Kariya and Joe Sakic.
In the 2018-19 regular season, O'Reilly set career-highs in assists (49), points (77) and plus/minus (plus-22). He finished the season as the League's top face-off man, winning 1,086 draws. In January, O'Reilly represented the St. Louis Blues at the 2019 NHL All-Star Game - his second appearance at the mid-season showcase.
Earlier this week,
O'Reilly was also nominated for the King Clancy Memorial Trophy
, given to players that exemplify leadership on the ice and have made significant humanitarian contributions to the community.
