The nykelharpa is a keyed fiddle traditional in Sweden. It is a string instrument or chordophone. Its keys are attached to tangents which, when the key is depressed, serve as frets to change the pitch of the string.

There are at least four major variants of the nyckelharpa still played today, varying by the number and arrangement of keys, number and arrangement of strings, and general body shape.

Some versions of the nyckelharpa have sympathetic strings which are not bowed directly but resonate with the other strings.