A syringe is provided which comprises a barrel (11) and a needle sheath (30) slidably located within the barrel, a plunger (20) with a plunger seal (23), a needle, a needle sheath (30) and a sheath seal (50), arranged so that depression of the plunger forces the needle sheath to move into a position where it covers or at least partly encloses the needle after delivery of fluid contents of the syringe. The needle sheath may be manually actuated or may be actuated by decompression of a spring. The syringe may further comprise a plunger disabling means operable to impede, prevent or otherwise hinder withdrawal of the plunger during or following depression of the plunger. The syringe may be a pre-filled syringe or a syringe which is filled by a user.