Nicklaus O'Leary (born August 31, 1992) is an American former professional football player who was a tight end in the National Football League (NFL). He played college football for the Florida State Seminoles, earning consensus All-American honors in 2014. He was selected by the Buffalo Bills in the sixth round of the 2015 NFL draft.

Nicklaus O'Leary is one of five children of Bill and Nan (Nicklaus) O'Leary.^[1][2] He attended Dwyer High School in Palm Beach Gardens, Florida, where he played football and lacrosse.^[1] He won state titles in both football and lacrosse. As a senior, he had 51 receptions for 875 yards and 12 touchdowns.^[3] Considered a four-star recruit by Rivals.com, he was listed as the top-ranked tight end recruit in his class.^[4]

As a true freshman in 2011, O'Leary played in all 13 games with two starts. He finished the season with 12 receptions for 164 yards and one touchdown. As a sophomore in 2012, he started 11 of 13 games, recording 21 receptions for 252 yards and three touchdowns. As a junior in 2013, he was a John Mackey Award finalist after recording 33 receptions for 557 yards with seven touchdowns.^[5] After considering entering the 2014 NFL draft, O'Leary returned to Florida State for his senior season.^[6] During his senior season, he set Florida State's record for career receptions for a tight end.^[7] He again was a finalist for the John Mackey Award, this time winning it.^[8] He was also named a consensus All-American.^[9] O'Leary finished the season with 48 receptions for 618 yards and six touchdowns.^[10] For his career, O'Leary had 114 receptions for 1,591 yards and 17 touchdowns.

In 2023, O'Leary joined Florida State as a student assistant coach, working with the offense. ^[24]

O'Leary's maternal grandfather is golfing legend Jack Nicklaus.^[25][26] Nick's father, Bill, was a highly recruited tight end who played at the University of Georgia, and his mother, Nan, played volleyball at Georgia.^[27]