William Branwhite Clarke (June 2, 1798 – June 17, 1878) was an English geologist.

Clarke was born at East Bergholt, in Suffolk. He received his early education at Dedham grammar school, and in 1817 entered Jesus College, Cambridge; he took his B.A. in 1821, was ordained and became MA, in 1824. In 1821 he was appointed curate of Ramsholt in Suffolk, and he acted in his clerical capacity in other places until 1839. Having become interested in geology through the teachings of Sedgwick, he utilized his opportunities and gathered many interesting facts on the geology of East Anglia which were embodied in a paper On the Geological Structure and Phenomena of Suffolk (Trans. Geol. Soc. 1837). He also communicated a series of papers on the geology of S.E. Dorsetshire to the Magazine of Nat. Hist. (1837-1838).

In 1839, after a severe illness, he left England for New South Wales, mainly with the object of benefiting by the sea voyage. He remained, however, in that country, and came to be regarded as the Father of Australian Geology. From the date of his arrival in New South Wales until 1870 he was in clerical charge first of the country from Parramatta to the Hawkesbury River, then of Campbelltown, and finally of Willoughby. He zealously devoted attention to the geology of the country, with results that have been of paramount importance. In 1841 he discovered gold, being the first explorer who had obtained it in situ in the country, finding it both in the detrital deposits and in the quartzites of the Blue Mountains, and he then declared his belief in its abundance. In 1849 he made the first actual discovery of tin in Australia and in 1859 he made known the occurrence of the diamond. He was also the first to indicate the presence of Silurian rocks, and to determine the age of the coal-bearing rocks in New South Wales. In 1869 he announced the discovery of remains of Dinornis in Queensland.

He was a trustee of the Australian museum at Sydney, and an active member of the Royal Society of New South Wales . In 1860 he published Researches in the Southern Gold-fields of New South Wales. He was elected F.R.S. in 1876, and in the following year was awarded the Murchison medal by the Geological Society of London. His contributions to Australian scientific journals were numerous. He died near Sydney.