William Paton Ker (usually referred to as "W. P. Ker"; 30 August 1855 - 17 July 1923) was a Scottish literary scholar and essayist.
He was born in Glasgow in 1855. He studied at Glasgow Academy, the University of Glasgow and Balliol College, Oxford.
He was appointed to a fellowship at All Souls College, Oxford in 1879. He became Professor of English Literature and History at the University College of South Wales, Cardiff in 1883; and moved to University College London as Quain Professor in 1889. He was the Oxford Professor of Poetry from 1920 to his death whilst hill-climbing in Europe. A W. P. Ker Memorial Lecture is held at Glasgow University in his honour.