Robert Langton Douglas (1 March 1864, Lavenham – 14 August 1951, Fiesole) was a British art critic, lecturer, and author, and director of the National Gallery of Ireland.

He was for years a University Extension lecturer, and for a time was in holy orders in the Church of England.

While a chaplain there, he wrote a monograph on Fra Angelico in consultation with various scholars, including Bernard Berenson.

In 1916 Douglas was appointed director of the National Gallery of Ireland in Dublin, but resigned in 1923 after a disagreement with its trustees.

Known chiefly as an authority on Sienese art, his most important publications are an edition of Crowe and Cavalcaselle's History of Painting in Italy (1903, et.