Art MacBaron O'Neill (sometimes referred to as Arthur O'Neill) (died 1618) was an Irish landowner and soldier of the Elizabethan and early Stuart eras. He was part of the O'Neill dynasty of Ulster, the illegitimate son of Matthew O'Neill, 1st Baron Dungannon. He was the half-brother of Brian O'Neill, Cormac MacBaron O'Neill and Hugh O'Neill, Earl of Tyrone. Art MacBaron (his middle name a reference to the title of his father) ruled over Oneilland south of Lough Neagh. He could speak fluent English unlike many of his relations.