W1

W1 could refer to:

* The London postal district W1
* 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. The term is derived from the Wolfenbüttel library which holds the manuscript. The other sources are W2, F1 (Florence), and Ma (Madrid).
*Dallas Semiconductor's 1-Wire bus