E40

E40 may refer to:

• Nimzo-Indian Defense, Encyclopaedia of Chess Openings code
• European route E40, a road extending from France to Kazakhstan
• E-40, a rapper
• GE E40, a locomotive
• a name for the fuel blend of 40% ethanol and 60% gasoline
• E40 screw, a type of Edison screw
• HMS E40, a British E class submarine