The triangle is an idiophone type of musical instrument in the percussion family. It is a bar of metal, usually steel in modern instruments, bent into a triangle shape.

The exact origins of the triangle instrument are unknown, but a number of paintings from the Middle Ages depict the instrument being played by angles, which has led to the belief that it played some part in church services at that time. Other paintings show it being used in folk bands.

In folk music, samba and rock music a triangle is more often hooked over the hand so that one side can be damped by the fingers to vary the tone. The pitch can also be modulated slightly by varying the area struck and by more subtle damping.