Harold William Taylor Wager FRS (11 March 1862 – 17 November 1929) was a British botanist and mycologist.
He was the uncle of the geologist Lawrence Rickard Wager.
He was made a Fellow of the Royal Society in 1904.
He was President of the British Mycological Society in 1910 and again in 1919.Wager was first a lecturer in botany at the Yorkshire College, then at Victoria University, then later he took the role of an Inspector of Schools for the Board of Education.