In phonetics, the airstream mechanism is the method by which airflow is created in the vocal tract. Along with phonation and articulation, it is one of three main components of speech production. The airstream mechanism is mandatory for most sound production and constitutes the first part of this process, which is called initiation.

The organ generating the airstream is called the initiator and there are three initiators used phonemically in non-disordered human oral languages:

There are also methods of making sounds that do not require the glottis. These mechanisms are collectively called alaryngeal speech mechanisms (none of these speech mechanisms are used in non-disordered speech):

Percussive consonants are produced without any airstream mechanism.

Any of the three principal initiators − diaphragm, glottis or tongue − may act by either increasing or decreasing the pressure generating the airstream. These changes in pressure often correspond to outward and inward airflow, and are therefore termed egressive and ingressive respectively.

Of these six resulting airstream mechanisms, four are found lexically around the world, alongside the percussive sounds produced without an airstream mechanism, for a total of five:

That leaves pulmonic ingressive and lingual (velaric) egressive as the only two airstream mechanisms produced by the three main initiators that are not found lexically in the world.

These mechanisms may be combined into airstream contours, such as clicks which release into ejectives.