James O'Neill (September 3, 1847June 9, 1929) was an American lawyer, jurist, and Republican politician. He served 24 years as a Wisconsin circuit court judge in western Wisconsin. Earlier, he had served one term in the Wisconsin State Assembly, representing Clark County.
Born in Lisbon, New York, O'Neill went to Lawrence University and later Cornell University where he graduated from in 1871. He taught school and studied law at Albany Law School, graduated in 1873, and was admitted to the New York Bar. In 1873, he moved to Neillsville, Wisconsin at the invitation of his uncle James O'Neill and practiced law. In 1885, he served in the Wisconsin State Assembly as a Republican. O'Neill was appointed District Attorney of Clark County, Wisconsin. He practiced law with Spencer M. Marsh until he was elected Wisconsin Circuit Court judge in 1897 serving until 1922. He was an unscucessful candidate in the 1906 Wisconsin Supreme Court election, placing second in a four-candidate race.
O'Neill died in Neillsville, Wisconsin on June 9, 1929.