Thomas Littleton Powys, the Fourth Baron Lilford (March 18, 1833 - June 17, 1896), was an English aristocrat and ornithologist.

He was one of the eight founders of the British Ornithologists' Union in 1858 and its President from 1867 until his death. He was also the first President of the Northamptonshire Natural History Society.

He travelled widely, especially in the Mediterranean Region and his extensive collection of birds was maintained in the grounds of his home, Lilford Hall, until 1991. His aviaries featured birds from around the globe, including rheas, kiwis, Pink-headed Ducks and even a pair of free-flying Lammergeiers. He was responsible for the introduction of the Little Owl into England in the 1880s.

He also wrote about birds. His books included Notes on the Birds of Northamptonshire and Neighbourhood (1895) and Coloured Figures of the Birds of the British Islands, which was completed by Osbert Salvin after his death.