The rebec (sometimes rebeck and originally various other spellings) is a bowed string musical instrument. In its most common form, it has three strings and is played on the arm or under the chin, like a violin. It was particularly popular in the 15th and 16th centuries.

The instrument is European, but probably developed from the Arabic instrument, the rabab. The rebec was first referred to by name around the beginning of the 14th century, although instruments very similar to it had been played since around the 10th century.

The rebec comes in a variety of slightly different forms, but is typically pear-shaped, with no clear division between the body and neck of the instrument, both being carved from the same single piece of wood. The body of the instrument is bowl-shaped, although the degree to which it is curved or flat can vary from instrument to instrument.

The rebec originally came in two basic forms: a wider instrument played under the chin; and a relatively narrower instrument which was rested on the player's thigh and played with the bow in an underhand position, like the viol. The under-the-chin technique had become predominant by the 15th century or so, but the instrument was narrower than before, and the bowl of the body less pronounced.

The number of strings on the rebec varies from one to five, although three is the most common number. The strings are often tuned in fifths, although this tuning is by no means universal. The instrument was originally in the treble range, like the violin, but later larger versions were developed, such that by the 16th century composers were able to write pieces for consorts of rebecs, just as they did for consorts of viols. However, the viol came to replace the rebec, and the instrument was little used beyond the renaissance period.

The instrument did remain in use by dance masters until the 18th century, however, often being used for the same purpose as the kit, a small pocket sized violin (also called a pochette or dancing masters violin). The rebec also continued to be used in folk music, especially in eastern Europe.