"Bill" Breed (August 3, 1928 – January 22, 2013) was an American geologist, paleontologist, naturalist and author in Northern Arizona.

After graduating from Massillon Washington High School, he served in the U.S. Army Corps of Military Police in South Korea and Japan (1946–48).

He married Carol S. Breed daughter of James Neilson (director) and Mrs. Ruth Swope (née Rogers) in 1965.

The couple had one daughter, Amelia, who joined the family of four girls (Linda, Laura, Grace, Pamela) from Carol's first marriage.

[citation needed] Bill Breed was a Fulbright Scholar at Canterbury University in Christchurch, New Zealand to study geomorphology in 1957–58.

In 1969, Breed and Edwin H. Colbert were two of the four vertebrate paleontologists in Antarctica who helped solidify the acceptance of continental drift theory, by finding a 220-million-year-old fossil of a Lystrosaurus.