William Leavitt Brann (c. 1877 – April 11, 1951) was an American businessman and Thoroughbred racehorse owner and breeder.
In partnership with Robert Stanley Castle, William Brann owned Branncastle Farm in Walkersville in Frederick County, Maryland.
Robert Castle's health problems, that led to his death in May 1948, saw him give up racing and William Brann then operated under the name Glade Valley Farm.
Brann owned a large number of runners during his years in racing including Escadru, Pictor, Vincentive, and Legendra.
Willam and Mabel Brann maintained a winter home in Boynton Beach, Florida where he died in 1951 at the age of seventy-three.