William Young Ottley was a British collector of and writer on art, amateur artist, and Keeper of the Department of Prints and Drawings at the British Museum. He was an early English enthusiast for 14th- and 15th-century Italian art, or the "Italian Primitives" as they were then often called. He spent the 1790s based in Rome, where he bought much art; this was sold for a considerable profit in 1801 after his return to London.

He was born near Thatcham, Berkshire, the son of an officer in the Guards. He became a pupil of George Cuitt the Elder, and studied in the Royal Academy of Arts Schools. In 1791 he went to Italy, and stayed there ten years, studying art and collecting pictures, drawings, and prints, profiting from the turmoil of the French invasion. On his return to England he raised large sums by auctioning his 16th- and 17th-century paintings at Christie's in May 1801 (the lots and prices are listed by Buchanan), but the earlier works would at that time have found little or no market in England. He became an arbiter of taste, and assisted collectors in the purchase of works of art and the formation of picture galleries. His own collection of drawings by Italian Old Masters he sold to Sir Thomas Lawrence, a close friend, for £8,000, and his print collection was also very fine. Paintings in his collection included The Mystical Nativity by Botticelli and Raphael's Vision of a Knight, both now in the National Gallery. In 1808 and 1812 he was living at No.43, Frith Street, Soho, London, and by 1818 in Kensington. He had one son, Henry Ottley, who died in Torquay (d. 3 February 1878).

In 1833 Ottley exhibited at the Royal Academy of Art, London an unfinished drawing of The Battle of the Angels. In the same year he was appointed Keeper of the Department of Prints and Drawings in the British Museum, a post he retained till his death in 1836. Some drawings are in the British Museum, which also has catalogues of two sales of his pictures, in 1811 and 1837.