W1
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.
 - McLaren W1, a sports car succeeding the F1 and P1
 - W-1, an experimental aircraft later known as the ERCO Ercoupe
 
 W-1 could refer to: