Horsham Museum is a museum at Horsham, West Sussex, in South East England. It was founded in August 1893 by volunteers of the Free Christian (now Unitarian) Church and became part of Horsham District Council in 1974.

We are a fully accredited museum and serve both Horsham and the wider district with the support of the Friends of Horsham Museum and an active volunteer base.

We have a large and varied collection arranged in 18 galleries.You can also find a significant collection of books and memorabilia relating to the Warnham-born poet Percy Bysshe Shelley (1792–1822), including many early editions of his works and that of his second wife Mary Shelley (1797–1851). We also possess original letters and books relating to the wider Shelley circle.

We own a number of prints by local artist John Guille Millais (1865–1931) along with a significant sculpture by Millais of fighting game birds that is now on permanent display.

Other collections include ceramics, ethnography, local Sussex trades and industries, working life, geology, archaeology, bicycles, and horses. A particular feature of the Museum's collections is the Archive of documents relating to Horsham and its history, including the collection of William Albery.

The Curator's Library has over 2,000 books on the Museum's collections and can be consulted upon request.