Isaac Dudley Fletcher (1844 – April 28, 1917) was an American businessman, art collector and museum benefactor. Native of Bangor, Maine, he settled in New York in 1865 and was a member of the Lotos and Union League clubs. He had the mansion built that is called today the Harry F. Sinclair House. He was president of Barrett Manufacturing Company and acquired a large art collection which he bequeathed to the Metropolitan Museum of Art.