HJ
# HJ

HJ may refer to:

## Science, technology, and mathematics

* Hall–Janko group, a mathematical group
* U.S. code for a cryptographic key change; see cryptoperiod

## Other uses

* ⟨hj⟩, a two-letter combination used in some languages
* hj-reduction in English, dropping the /h/ sound before /j/
* Hajji (Hj.), an Islamic honorific
* Handjob
* hic jacet ('here lies'), Latin phrase on gravestones
* Hilal-i-Jurat, post-nominal for Pakistan honour
* Hitler-Jugend (Hitler Youth)
* Holden HJ, an Australian car 1974-1976
* Hot Jupiter, a type of planet
* Tasman Cargo Airlines, IATA airline designator
