William Daniel Conybeare FRS, dean of Llandaff, was an English geologist, palaeontologist and clergyman. He is probably best known for his ground-breaking work on fossils and excavation in the 1820s, including important papers for the Geological Society of London on ichthyosaur anatomy and the first published scientific description of a plesiosaur.

Ichthyosauria is an order of large extinct marine reptiles sometimes referred to as "ichthyosaurs", although the term is also used for wider clades in which the order resides.