Simms-Watts is a British amplifier brand founded in 1968 by Ealing music-shop owner David Simms and technical director Richard Watts, with early design contributions from Terry Marshall (son of Jim Marshall). The company launched a line of high-headroom valve instrument and PA amplifiers that competed directly with Marshall, Hiwatt, and Sound City during the early 1970s, before EMI Sound & Vision acquired the operation in 1972 and eventually wound it down as production shifted toward cost-reduced solid-state designs.

The brand is best known for its ultra-linear tube heads, particularly the AP100 (an EL34-powered 100-watt head) and the AP200 / PA200 'Super' (a KT88 quad in the same lineage as the Marshall Major and Hiwatt DR201), along with bass-oriented models such as the GE100. Simms-Watts heads have developed a cult following for their loud, clean headroom and rugged British voicing, and are associated with players like John Entwistle and Mick Ronson, who were spotted using the amps during their peak era.

The name was later revived by a Nashville, Tennessee-based workshop building hand-wired all-tube amplifiers inspired by the original British circuits, keeping vintage Simms-Watts designs such as the AP100 in production for modern players.

Simms-Watts has 2 products cataloged on Equipboard, including Guitar Amplifier Heads and Guitar Amplifier Cabinets. Their gear is featured by 2 artists, with the strongest followings in Rock. Notable users include John Entwistle and Paul Rudolph.