W1 could refer to:

• W1, a postcode district in the W postcode area of London
• British NVC community W1 (Salix cinerea - Galium palustre woodland), one of the woodland communities of the British National Vegetation Classification
• W-1 tool steel, a water-hardening steel
• one of four manuscripts containing the Magnus Liber, or Magnus liber organi, a compilation of medieval music. The term is derived from the Wolfenbüttel library which holds the manuscript (Herzog August Bibliothek).
• GN W-1, an electric locomotive built for the Great Northern Railway
• LNER Class W1, an experimental locomotive designed by Sir Nigel Gresley for the London and North Eastern Railway
• second step of the W0-W6 scale for the classification of meteorites by weathering
• Wrestle-1, a Japanese professional wrestling promotion
• The computational complexity class W[1] in parameterized complexity
• The Apple W1 wireless pairing chip primarily used in AirPods
• W1 tram, a class of electric trams built by the Melbourne & Metropolitan Tramways Board.

W-1 could refer to:

• U.S. uniformed services pay grades#Warrant Officer pay grades