Sir William John Pugh OBE FRS (28 June 1892 – 18 March 1974) was a British geologist who was director of the Geological Survey of Great Britain and of the Museum of Practical Geology, Department of Scientific and Industrial Research.^[2]

He was born in Westbury, Shropshire, the only son of coal merchant John Pugh and educated at Welshpool County School and the University College of Wales, Aberystwyth, where he graduated BA in Geography in 1914.^[3] However, he was inspired to study geology by Professor Owen Thomas Jones. In 1915, they presented their first joint study (of the geology of the area around Machynlleth) to the Geological Society of London.^[2]

During World War I, he served with the Royal Welch Fusiliers as a staff officer, rising to the rank of major. He was appointed an Officer of the Order of the British Empire (OBE) in the 1919 New Year Honours,^[4] awarded the French Croix de Guerre and was twice mentioned in despatches.

After the war he returned to University College as Professor of Geology from 1919 to 1931, acting as Dean of the Faculty of Science from 1929 to 1931. During this time he carried out field studies to map the chronostratigraphy of the ancient Ordovician-Silurian rocks of the Corris and Bala districts and in 1928 was awarded a DSc by the University of Wales.

In 1931 he was appointed Professor of Geology and Director of the Geological Laboratories at the University of Manchester, a post he held until 1950. He served as Dean of the Faculty of Science there from 1939 to 1941, as Pro-Vice Chancellor from 1941 to 1943 and as Deputy Vice-Chancellor from 1943 to 1950. As a member of the Inter-University Council for Higher Education in the Colonies he went to Malaya in 1947 with the Commission on Higher Education to advise on university development there. He was elected president of Section C (Geology) of the British Association for the Advancement of Science (1948–49).^[5]

In 1951 he was made Emeritus Professor when he resigned to become Director of the Geological Survey of Great Britain and of the Museum of Practical Geology (1951–60). He commenced the task of producing a geological map of the country and was also responsible for the Water Department and the Atomic Energy Division. The activities of the institution included the undertaking of field studies in six other countries across the world for the Atomic Energy Division and an aeromagnetic survey of England and Wales, which involved surveying the Cheshire salt fields and the mapping of coalfields and advisory work for the National Coal Board, the Scottish Hydro-electric Board and the Ministry of Housing. He published many papers in scientific journals reporting on the progress of this work.