The tin whistle, also known as the penny whistle, is a simple six-holed woodwind instrument. It is a type of fipple flute, putting it in the same class as the recorder, Native American flute, and other woodwind instruments that meet such criteria. A tin whistle player is called a whistler. The tin whistle is closely associated with Irish traditional music and Celtic music. Other names for the instrument are the flageolet, English flageolet, Scottish penny whistle, tin flageolet, or Irish whistle.

The term fipple specifies a variety of end-blown flute that includes the flageolet, recorder, and tin whistle. The Hornbostel–Sachs system for classifying musical instruments places this group under the heading "Flutes with duct or duct flutes." The label "fipple flute" is frequently applied to members of the subgroup but there is no general agreement about the structural detail of the sound-producing mechanism that constitutes the fipple, itself.