Sir Thomas Newenham Deane (1828 – 8 November 1899) was an Irish architect, the son of Sir Thomas Deane and Eliza Newenham, and the father of Sir Thomas Manly Deane. His father and son were also architects. Works attributed to Thomas Newenham Deane, and his architectural practice, include the National Library of Ireland, a wing of the National Gallery of Ireland, St Mary's Cathedral, Tuam, the Kildare Street Club, and a number of buildings in the Trinity College Dublin campus.