Gillian Horst enters her first season as an assistant coach for the Williams College women's lacrosse program during the 2026-27 academic year.

Horst played collegiate lacrosse at Little Three-rival Wesleyan in Middletown, Connecticut, from 2019-23, as she compiled 50 goals, 14 assists and 64 points, to go along with 66 draw controls, 52 ground balls and 21 caused turnovers. She served as a captain during her senior season and appeared in 46 games during her career, making 44 starts.

Horst was named to the Intercollegiate Women's Lacrosse Coaches Association (IWLCA) All-Berkshire Region First and Second Team in 2021 and 2022, respectively, while also taking home NESCAC All-Conference Second Team laurels during the 2021 season. The 2022 and 2023 Cardinal teams reached the Sweet 16 of the NCAA Division III Tournament. Horst also competed for the women's soccer team at Wesleyan during her first year in 2019.

Horst graduated from Wesleyan in 2023 with a Bachelor of Arts in neuroscience and behavior, while minoring in quantitative analysis. She served the community as a Harlem Lacrosse tutor and spent time working with Nike Lacrosse camps on Cape Cod from 2021-22, guiding and developing players on a team and individual level, organizing and designing drills, and establishing an engaging environment.

Prior to joining Williams, Horst spent time as an assistant girls' varsity lacrosse coach at the National Cathedral School in Washington, D.C., since January 2025. She assisted with practice planning and execution, led small group sessions in the offseason to improve stick skills, lacrosse IQ and game mechanics, and utilized film for scouting and player-learning purposes.