A gas syringe is a piece of laboratory glassware used to insert or withdraw a volume of a gas from a closed system, or to measure the volume of gas evolved from a chemical reaction. A gas syringe can also be used to measure and dispense liquids, especially where these liquids need to be kept free from air.

A gas syringe has an inner syringe chamber which has a ground glass surface. The syringe barrel also has a ground glass surface. The ground surface of the barrel moves freely within the ground glass surface of the syringe chamber with very little friction. The close mating of these ground glass surfaces also gives a reasonably gas-tight seal. Like a ground glass stopcock, the two parts of a gas syringe should preferably not be interchanged with another gas syringe of the same volume, unless told otherwise by the distributor. Gas syringes come in various sizes from 500 ml to 0.25 ml and tend to be accurate to between 0.01 and 1 ml, depending on the size of the syringe.