Dutch lichenologist (1894-1965).
Pieter Groenhart (21 February 1894 – 3 November 1965) was a Dutch lichenologist known for his research into tropical Asian lichens. After beginning his career as a teacher in the Netherlands, he relocated to the Dutch East Indies (present-day Indonesia) in 1926, where he taught while developing his expertise in lichenology. During World War II, he was interned by Japanese forces for three years, suffering health consequences including vision impairment. Following the war, he worked at the Rijksherbarium in the Netherlands and later at the Herbarium Bogoriense in Indonesia until 1954. Groenhart