Reginald Heber Fitz (May 5, 1843 – September 30, 1913) was an American physician known for his research on abdominal disorders.

In 1886, he published "Perforating Inflammation of the Vermiform Appendix; With Special Reference to Its Early Diagnosis and Treatment".

This groundbreaking paper provided analysis of 466 cases of abdominal disorders that had previously been variously diagnosed and showed that they all involved a diseased appendix.

He also served as physician to the Boston Dispensary in 1871–1882 and to the Massachusetts General Hospital from 1887 to 1908.

[1] He died in Brookline, Massachusetts, on September 30, 1913, after having surgery to remove a gastric ulcer.