Justice O'Neill may refer to:
C. William O'Neill (1916–1978), associate justice and chief justice of the Ohio Supreme Court Harriet O'Neill (born 1957), associate justice of the Supreme Court of Texas William O'Neill (Ohio judge) (born 1947), associate justice of the Ohio Supreme Court
See also Charles Austin O'Niell (1869–1951), associate justice of the Louisiana Supreme Court John Belton O'Neall (1793–1863), judge on the precursor of the South Carolina Supreme Court Lawrence O'Neil (born 1954), associate chief justice of the Nova Scotia Supreme Court Justice Neil (disambiguation)