The son of an architect, Harold Knight was born in Nottingham and studied at the Nottingham School of Art where he met fellow artist, Laura Johnson, whom he married in 1903. He spent time studying in Paris under Jean-Paul Laurens and Benjamin-Constant, and in Staithes in North Yorkshire. He also made several trips to Holland where he became interested in the farming subjects and interiors of simple peasant living, painting in the manner of The Hague School.
In 1907, Knight moved to Newlyn in Cornwall with his wife where they became part of the famous Newlyn School. The Knights remained in Cornwall until 1919 where Harold painted genre subjects with a light palette. Following the First World War, the Knights moved to London although they frequently returned to Cornwall to paint. Whilst living in London, he painted portraits of many of the well-known cultural and political figures of the period. In 1925, he received a Silver Medal at the Paris Salons and, in 1931, he was elected a member of the Royal Academy.