Ealing Common Depot is a London Underground railway depot on the District line, located between Acton Town and Ealing Common stations in west London, England. It is one of the oldest main depots on the Underground, having been built in 1905, when the District Railway was upgraded for electric traction. All depot facilities were moved there from Lillie Bridge Depot, and it was known as Mill Hill Park Works. It subsequently became Ealing Common Works, and its status was reduced to that of a depot in 1922, when Acton Works was opened, and took over responsibility for all major overhauls. Most of the functions of Acton Works were devolved back to the depots, including Ealing Common, in 1985.