Senator O'Neil or O'Neill may refer to:
Jerry O'Neil (politician) (born 1943), Montana State Senate William T. O'Neil (1850–1909), New York State Senate William O'Neil (Wisconsin politician) (1848–1917), Wisconsin State Senate Bill O'Neill (New Mexico politician), New Mexico State Senate Charles O'Neill (Pennsylvania politician) (1821–1893), Pennsylvania State Senate Edward J. O'Neill (Rhode Island politician), Rhode Island State Senate Edward O'Neill (Wisconsin politician) (1820–1890), Wisconsin State Senate Héctor O'Neill (born 1945), former member of the Senate of Puerto Rico Isabelle Ahearn O'Neill (1880–1975), Rhode Island State Senate James O'Neill (Washington politician) (1824–1913), Washington State Senate John O'Neill (congressman) (1822–1905), Ohio State Senate Lottie Holman O'Neill (1878–1967), Illinois State Senate Deborah O'Neill (born 1961), member of the Australian Senate