Humphry Waldo Sibthorp (1713–1797) was a British botanist. After the death of Johann Jacob Dillenius (1684–1747), he became the Sherardian Professor of Botany at the University of Oxford from 1747 to 1783; he is famous for having taught one course for 37 years. He began the catalogue of the plants of the botanical garden of the university, Catalogus Plantarum Horti Botanici Oxoniensis. His youngest son was the well-known botanist John Sibthorp (1758–1796), who continued the Catalogus Plantarum. The genus Sibthorpia, in the plantain family of plants is named after him.