Ilgenfritz is a surname. Notable people with the surname include: Alice Ilgenfritz (1846–1906), American writer and novelist Charles H. Ilgenfritz (1837–1920), American Civil War soldier James Ilgenfritz (born 1978), American composer, bassist, and multi-instrumentalist Mark Ilgenfritz (born 1952), American football defensive end William Ilgenfritz (1946–2026), American Anglican bishop Wolfgang Ilgenfritz (1957–2013), Austrian politician