Saltpeter (or saltpetre) is the mineral form of potassium nitrate (KNO3), a chemical compound.

It may also sometimes refer to:

Sodium nitrate (NaNO3), a compound Chile saltpeter or nitratine, the mineral form Norwegian saltpeter or calcium nitrate (Ca(NO3)2) Magnesium nitrate (Mg(NO3)2)

See also Saltpetre Republic, a term used in Chilean historiography for the 1879–1914 period Salpeter (disambiguation)