Eliza O'Neill (1791 – 29 October 1872) was an Irish actress, later baronetess.
Born in Drogheda, she was the daughter of an actor and stage manager. Her first appearance on the stage was made at the Crow Street theatre in 1811 as the Widow Cheerly in Andrew Cherry's The Soldier's Daughter, and after several years in Ireland she came to London and made an immediate success as Juliet at Covent Garden in 1814. For five years she was the favorite of London town in comedy as well as tragedy, but in the latter she particularly excelled, being frequently compared, not to her disadvantage, with the great Sarah Siddons.
In 1819 she married William Wrixon Becher, an Irish M.P., who was to be created a baronet in 1831. She never returned to the stage, and died in 1872.