William Richard Lethaby was born on January 18, 1857, in Barnstaple, Devon, England.

He was an English architect, designer, educator, and architectural theorist and historian. After studies at Barnstaple Art School and an early apprenticeship with a local architect, he found work in London in 1879 as Chief Clerk to architect Richard Norman Shaw. Shaw quickly recognized Lethaby's talent as a designer. He contributed significant pieces of work to major Shaw-designed buildings, e.g., Scotland Yard in London and Cragside in Northumberland. Lethaby became involved in the Society for the Protection of Ancient Buildings, which campaigned to preserve the integrity and authenticity of older buildings. He was a co-founder of the Art Workers Guild in 1884. In 1889, he started to practice independently, designing a wide range of products, e.g., books, furniture, stained glass as well as many buildings, exploring the mystical symbolism of medieval and non-European design and architecture. He published the book "Architecture, Mysticism, and Myth" (1891). In 1894, Lethaby was appointed Art Inspector to the Technical Education Board of the newly formed London County Council. He founded the Central School of Arts and Crafts in 1896. In 1901, he was appointed the first Professor of Design at the Royal College of Art. He also served as Principal of the Central School of Arts and Crafts in 1902 and Surveyor of Westminster Abbey in 1906. He became increasingly devoted to the academic study of the theory and history of architecture and design.

In 1901, he married Edith Rutgers Crosby (1851-1927). He died on July 17, 1931, in Bayswater, Middlesex, England.