Brian Lowdermilk (born December 14, 1982) is an American musical theater composer and lyricistBrian Lowdermilk is a composer and lyricist of musicals. He is also a music director, arranger, vocal coach, and pianist. He is an alumnus of NYU and BMI theatre writing workshop, and CEO of start-up, NewMusicalTheatre.com.

Lowdermilk is best known for his collaborations with Kait Kerrigan. Their works together include shows such as The Bad Years, Republic, Unbound, Flash of Time, The Woman Upstairs, The Unauthorized Autobiography of Samantha Brown (with Zach Altman) and Wrong Number. Lowdermilk and Kerrigan wrote TheatreworksUSA's adaptation of Henry and Mudge, which premiered Off-Broadway in 2006 at the Lucille Lortel Theatre, which is where he made his Off-Broadway debut. In one review of that piece, Lowdermilk and Kerrigan were called "perhaps the most important young writers in musical theatre today."