Jayne Brook (born September 16, 1960) is an American actress, best known for her roles as Dr. Diane Grad on the medical drama Chicago Hope, as a series regular for five of the show's six seasons, and Mary Ann Mitchell on The District from 2000 to 2002. Between 2017 and 2019, Brook had a recurring role as Starfleet Vice Admiral Katrina Cornwell in the series Star Trek: Discovery.