GJ or Gj may refer to:
- Gj (letter), a Latin digraph
- Generic Java, a programming language
- Gharjamai, a live-in Son-in-Law
- Gigajoule, a unit of energy
- Eurofly's IATA code
- Mexicargo's IATA code
- GJ, a prefix for Gliese Catalogue of Nearby Stars star catalogue references
- Good job (phrase)