Sebastien O'Neill is an assistant coach for the University of Delaware track and field and cross country programs in Newark, Delaware, where he joined the staff before the 2024-25 season and began overseeing the sprints, jumps, and multis groups on Aug. 5.
In his first year at Delaware, his event groups produced 24 additions to the program's all-time top-10 lists, including a pentathlon school record by Sara Manson. Manson also won bronze in both the pentathlon and heptathlon at the indoor and outdoor CAA Championships. During the 2025-26 track season, Delaware earned five all-conference honors, with Lauren Leath winning the 400 hurdles and Olamide Ayeni winning the discus to become the first Blue Hens in program history to capture their events at the CUSA Championships.
