Granahan is a surname. Notable people with the surname include: Gerry Granahan (1932–2022), American singer, songwriter, and record producer. Kathryn E. Granahan (1894–1979), Democratic member of the U.S. House of Representatives from Pennsylvania. William T. Granahan (1895–1956), Democratic politician from the U.S. state of Pennsylvania https://en.wikipedia.org/wiki/Granahan