QED can mean several different things:

• Q.E.D. Latin Quod erat demonstrandum, used at the end of mathematical proofs
• The QED project intended to construct a formalized database of all mathematical knowledge
• The QED text editor program
• Quantum electrodynamics, a field of physics
• Quantum Effect Devices, a maker of MIPS architecture microprocessors which was acquired by PMC-Sierra in 2000.
• QED (book) (1985), by Richard Feynman
• QED (play) , by Peter Parnell about Richard Feynman
• Q.E.D. (1903), by Gertrude Stein, published as Things As They Are (1973)
• Q.E.D. (manga) , a detective manga by Katou Motohiro .
• Quantum Explosion Dynamo, an object in the computer game Commander Keen