Robert E. "Bob" Holthus (June 24, 1934 – November 22, 2011) was an American Thoroughbred racehorse trainer. As a second generation trainer, Holthus learned the profession from his father, Paul Holthus. Holthus is the all-time winningest trainer at Oaklawn Park and as of 2005 had won nine trainer's titles there. He also won training titles at Chicago's Arlington Park and Hawthorne Race Course, the Detroit Race Course, Ellis Park Racecourse in Henderson, Kentucky, Louisiana Downs in Bossier City, Louisiana plus a fall meeting at Turfway Park in the suburbs of Cincinnati, Ohio.