The viola pomposa (also called the violino pomposo) is a five-stringed viola that was created around 1725. There are no exact size rules for all instruments called by this name, but in general, the pomposa is slightly wider than a standard viola (which explains the Italian word "pomposa," meaning "proud" or "grand"). It uses four strings tuned like a regular viola (C-G-D-A) and adds a high E string, usually from a violin. This gives the instrument a larger range than a standard viola. The sound is slightly more resonant than a violin. The viola pomposa is held on the arm and can play notes from C3 to A6 (or higher) when using fingers. With harmonics, the range can reach as high as C8, depending on the quality of the strings.

The viola pomposa should not be confused with the viola da spalla, the violoncello, or the violoncello piccolo, even though these instruments sometimes had similar roles in Baroque music ensembles. Scholars debate where the viola pomposa originated. Some believe Johann Sebastian Bach invented it, as suggested by musicologists like Philipp Spitta. However, others, such as Charles Sanford Terry and Dmitry Badiarov, argue there is not enough evidence to support this claim.

Late Baroque and early Classical composers who used the viola pomposa include Georg Philipp Telemann (1681–1767; two sections of Der Getreue Musikmeister), Johann Gottlieb Graun (c. 1703–1771; a double concerto with flute), and Christian Joseph Lidarti (1730–1795; at least two sonatas).

By 1800, the viola pomposa was played by principal musicians in major orchestras, though no written scores from that time were published, except for older or updated editions (such as a heavily edited version of one of Lidarti’s sonatas, republished around 1904).

In the late twentieth century, modern composers rediscovered the instrument because of new synthetic and steel strings, which are more stable and less expensive than older gut strings. Recent works for the viola pomposa include compositions by Justin E.A. Busch, Harry Crowl, Rudolf Haken, and Zoltan Paulinyi.