William Phillimore Watts Phillimore (formerly Stiff) MA BCL (1853–1913) was an English solicitor, genealogist and publisher.
William Phillimore Watts Stiff was born on 27 October 1853 in Nottingham, the eldest son of Dr William Phillimore Stiff M.B. Lond., M.R.C.S. Eng., of Sneinton, Nottingham, afterwards superintendent of Nottingham General Lunatic Asylum, and Mary Elizabeth, daughter of Benjamin Watts of Bridgen Hall, Bridgnorth, Shropshire. In 1873 William Stiff senior changed the family surname by royal licence to Phillimore, his great-grandmother's maiden name. William junior studied at The Queen's College, Oxford, and was awarded a second-class degree in Jurisprudence in 1876.