W40

W40 may refer to:


 * W40 (nuclear warhead)
 * Kembuchi Station, in Hokkaido, Japan
 * Ngarla language
 * Nissan Civilian (W40), a minibus
 * Wanderer W40, a sedan
 * Westerhout 40, a star-forming region
 * W 40, a classification in masters athletics
 * W40, a Toyota W transmission