A42

A42 may refer to :
 * A42 road (England), a road connecting Kegworth and Appleby Magna
 * A42 road (Northern Ireland), a road connecting Maghera and Carnlough
 * A42 motorway (France), a road connecting Lyon and Pont-d'Ain
 * A 42 motorway (Germany), a road connecting Kamp-Lintfort and Castrop-Rauxel
 * A-42 motorway (Spain), a road connecting Madrid and Toledo

A.42 may refer to :
 * Aero A.42, a Czechoslovakian bomber aircraft of 1929 that was only ever produced in prototype form
 * A42 tank, a British War Office designation for the "Heavy Churchill" (Mk.XIII) tank