William Hellier Baily (7 July 1819 – 6 August 1888) was an English palaeontologist.

[1] From 1837 to 1844 he was Assistant Curator in the Bristol Museum, a post he relinquished to join the staff of the British Geological Survey in London.

[2] In 1857 he was transferred to the Irish branch of the Geological Survey, as acting palaeontologist, and retained this post until the end of his life.

[1] He was the author of many papers on palaeontological subjects,[3] and of notes on fossils in the explanatory memoirs of the Geological Survey of Ireland.

He published (1867–1875) a useful work entitled Figures of Characteristic British Fossils, with Descriptive Remarks, of which only the first volume, dealing with palaeozoic species, was issued.