English Baptist missionary and West African explorer.

In 1874 the Baptist Missionary Society assigned Grenfell to the Cameroons, where he undertook various explorations. Transferring to the Congo in 1878, Grenfell established new mission stations, through which he helped to undo the ravages of the slave trade. With a small ship, he made exploratory voyages up the Congo (1884–87) and Aruwimi (1900–02) rivers. For his exact observations, he was awarded the Founder's Medal of the Royal Geographical Society in 1887.