Grey or gray box may refer to:

• Gray box testing, software testing
• Grey box model, in mathematics, statistics, and computational modelling
• Grey identification method, used in system identification

• Jojoba (Simmondsia chinensis), also known as gray box bush

• Grey box, many trees in the genus Eucalyptus, native to Australia, including:
  • Eucalyptus argillacea (Kimberley grey box or northern grey box)
  • Eucalyptus bosistoana (coast grey box or Gippsland grey box)
  • Eucalyptus brownii (grey box)
  • Eucalyptus hemiphloia (grey box); See Eucalyptus albens
  • Eucalyptus largeana (grey box)
  • Eucalyptus microcarpa (grey box, inland grey box or western grey box)
  • Eucalyptus moluccana (grey box or coastal grey box)
  • Eucalyptus normantonensis (grey box)
  • Eucalyptus pilligaensis (narrow-leaved grey box, pilliga grey box)
  • Eucalyptus quadrangulata (grey box)
  • Eucalyptus rummeryi (grey box)
  • Eucalyptus tectifica (grey box)