Robert Sydens Doak (March 16, 1881 – July 1, 1942) was an American football, basketball, and baseball coach. His stops included Elon University, Duke University, and Guilford College. Doak also served as Elon's and Guilford's athletic director during his tenures at the school. He was succeeded by his brother, Chick Doak, as Duke's head basketball coach in 1916.