David Andrew Thornley (31 July 1935 – 18 June 1978) was an Irish Labour Party politician and university professor at Trinity College Dublin.

His PhD was entitled "Isaac Butt and the creation of an Irish parliamentary party (1868–1879)" and was written under the supervision of Theodore William Moody.

[1] He confronted the party leader Brendan Corish, who at the time of the Arms Crisis reportedly rejected out of hand any suggestion of military aid or use of force after the outbreak of violence in Northern Ireland.

[7] In April 1976, he lost the Labour party whip after appearing on Sinn Féin platform during Easter Rising commemorations.

[1] In 1978 he joined the newly formed Socialist Labour Party stating that he had done so because: "There is no man in politics that I respect more than Noël Browne, despite our occasional differences.