Polyfusion is an analog synthesizer manufacturer based in the Buffalo, New York area. The company was founded in the mid-1970s by Ron Folkman and Alan Pearce, both of whom previously worked at Moog Music before striking out to build what they envisioned as a successor to the Moog modular system. Their flagship product, the Series 2000 modular synthesizer, was a large-format instrument produced in extremely limited numbers — only around thirty complete systems were ever built — which gave it cult status among collectors of vintage modular gear.

After the original Series 2000 era, the company shifted away from musical instruments and focused on custom electronic systems and design work, while continuing to service vintage Polyfusion gear. A revival of the brand was announced at Knobcon 2018, with Folkman returning to develop the Series 3000, a reissue concept aimed at shrinking the depth and width of the original modules while preserving the sound and design philosophy of the Series 2000. The Series 3000 is not built to the Eurorack format.

Notable Series 2000 owners have included Steve Porcaro of Toto, whose 1979 system has been documented in restoration projects, and Vince Clarke of Erasure, whose Polyfusion system became part of a noted private synth collection.

Polyfusion has 2 products cataloged on Equipboard, including Effects Processors and Modular Synthesizers. Their gear is featured by 3 artists, with the strongest followings in Rock, Electronic, and Pop. Notable users include Vince Clarke, Steve Porcaro, and Kid Koala.