William De Alwis Seneviratne (1842–1916) was a Ceylonese artist and entomologist.

[1] With his brother George (dates unknown), William made a lasting contribution to the knowledge of the lepidoptera (butterflies and moths) of Ceylon.

William was appointed to succeed him to continue the work as a botanical artist.

George Thwaites, the Director of the Botanical Garden at Peradeniya between 1849 and 1879, who was impressed by the de Alwis brothers' botanical drawings, recommended to W H Gregory, the Governor of Ceylon, that they should draw from nature the butterflies and moths of Ceylon.

The drawings were accurate and later used by a number of authors publishing on the lepidoptera of Ceylon, notably by George Morrison Reid Henry and L G O Woodhouse.