L42

L42 may refer to:
 * HMS Brocklesby (L42), an ex-coaster taken up from trade that served in World War I for the British Royal Navy
 * Lee–Enfield L42, a sniper rifle
 * Mitochondrial ribosomal protein L42, a human protein
 * Sako Model L42, a rifle
 * Spanish landing ship Pizarro (L42)
 * an engine in GM's Ecotec engine family
 * a version of the Chaika L-4 amphibian aircraft