Sir Gerald or Gerard Lally or O'Mullally (Tuam, County Galway - 1737) was an Irish Jacobite and French military officer. He was the second son of Thomas Lally (or O'Mullally) of Tullaghnadaly, by his wife, Jane, sister of Theobald Dillon, 7th Viscount Dillon, and younger brother of James Lally. He served with James II's forces in Ireland, and after the end of the Siege of Limerick (1691) he fled to France. His grandson was Gérard de Lally-Tollendal.