GuitarSystems is a Dutch effects pedal maker founded in 2000 by Paul Lenders, a guitarist who began the company around his Buffer circuit design and PaulSwitch footswitch. Circuit designer Ad Van Dongen — credited as N.E.R.D. — joined as principal engineer in 2007 and is responsible for much of the analog circuit work. The pedals are hand-built in the Netherlands and target pro players looking for vintage-voiced tones in road-worthy enclosures.

The core catalog consists of a handful of classic circuits offered in Junior (1590B) and Standard (125B) format, including the DriveTool (a CMOS-based overdrive/fuzz), FuzzTool (germanium Fuzz Face voicing), Tony's BenderTool (germanium Tone Bender MkII), TrebleTool (germanium Rangemaster-style treble booster), and VibeTool (photocell Uni-Vibe). Standard-format versions add impedance switching and further circuit refinements, and most pedals share a TFM (Treble Full Mid) EQ control.

The brand has built a low-profile reputation as a pro-tier boutique option, with users including Brian Ray, Matthew Bellamy, Mark Tremonti, Nils Lofgren, Steve Stevens, Dave Kilminster, Tim Pierce, and Simon Neil.

GuitarSystems has 4 products cataloged on Equipboard, including Univibe & Rotary Effects Pedals, Fuzz Effects Pedals, and Boost Effects Pedals. Their gear is featured by 7 artists, with the strongest followings in Rock, Pop, and Electronic. Notable users include Steve Stevens, Sean Lennon, and Brian Ray.