PIW may refer to:
Public Interest Watch, a US group that claims to fight charitable trust abuse Pikwitonei Airport, the IATA code for the airport in Canada PIW or Państwowy Instytut Wydawniczy (State Publishing Institute), Polish publishing house founded in 1946 pounds per inch width, an imperial measure Person in water, a term used by water rescue teams in the case of a Man overboard.
pl:PIW