Sir Alexander MacDonnell, 1st Baronet (1794–1875) was an Irish civil servant, commissioner of national education in Ireland.
He gained a king's scholarship at Westminster School in 1809, and was elected in 1813 to Christ Church, Oxford, where he held a studentship until 1826.
He was called to the bar at Lincoln's Inn, 23 November 1824, went the midland circuit, attended the Leicester and Northampton sessions, and served as a commissioner of inquiry into public charities.
He was made a privy councillor of Ireland in 1846, resigned his commissionership in December 1871, and was created a baronet 20 January 1872.
He married in 1826 Barbara, eldest daughter of Hugh Montgomery of Benvarden, County Antrim, and widow of Richard Staples.