E91 may refer to:
*
E91 protocol, a protocol of Quantum Cryptography
*
E91, a car of the BMW 3 Series
*
King's Indian Defense, Encyclopaedia of Chess Openings code
*
European route E91, one of the many routes in the
European route network.
*
Minami-Hanna Road and Yamatotakada Bypass, route E91 in Japan.
{{Letter-NumberCombDisambig