D40

D40 may refer to:
 * Akaflieg Darmstadt D-40, a German sailplane
 * D40 Navara, a Nissan pickup truck
 * D40 road (Croatia)
 * Dupuy D-40, a French monoplane
 * HMS Searcher (D40), a Ruler-class escort carrier of the Royal Navy
 * LNER Class D40, a class of British steam locomotives
 * New Flyer D40, a Canadian bus
 * Nikon D40, a digital camera