Quasimidi Musikelektronik GmbH was a German synthesizer manufacturer founded in 1987 by Friedhelm Haar and Jörg Reichstein. Based in Hesse — originally in Kirchhain, later relocating to Rauschenberg — the company built a reputation in the 1990s for hardware aimed squarely at electronic dance music producers.

The company's first widely recognized product was the Quasar, a rack-mounted digital synthesizer module released in 1993. Quasimidi went on to become one of the early modern manufacturers to bring tactile knobs, lit buttons, and dedicated controls back to synthesizer front panels, most prominently with the Rave-O-Lution 309, a groovebox combining a pattern sequencer with drum and bass-synth sections that competed with Roland's MC-303. A keyboard version called the Sirius added a built-in vocoder, and the Raven offered a full-size sample-based virtual analog with an unusual sequencer that let keys be used for muting and transposition.

Quasimidi's final product was the Polymorph, a multitimbral synth-and-drum machine pitched at electronica producers and considered a successor to the Rave-O-Lution. The company ceased operations in 2000, but its instruments — particularly the 309, Sirius, and Polymorph — remain sought after on the secondhand market by producers of techno, trance, and other electronic styles.

Quasimidi has 9 products cataloged on Equipboard, including Synthesizers and Modular Synthesizers. Their gear is featured by 15 artists, with the strongest followings in Electronic, Rock, and Pop. Notable users include Klaus Schulze, Trent Reznor, and Kraftwerk.