MJM Guitar FX is a boutique effects pedal builder founded in 1998 by Mike Milcetic, originally based in Montreal. The company began when Milcetic set out to build a backup for his vintage Fuzz Face, and grew into a small operation focused on hand-built recreations of classic 1960s and 1970s effect circuits using period-correct components such as germanium transistors.

The lineup centers on vintage-voiced fuzz, octave fuzz, vibe, wah, boost, and overdrive pedals. Notable models include the London Fuzz (a germanium Fuzz Face-style unit and the brand's flagship since 2000), the Foxey Fuzz, the Roctavios octave fuzz, the Sixties Vibe (a Univibe-style chorus/vibrato), the BritBender, the Phantom Overdrive, and the Mavis Wah. Pedals are sold direct through the company's website and through specialty boutique retailers.

MJM Guitar FX has built a steady reputation in the boutique pedal community for chasing authentic vintage tones rather than chasing trends, and its pedals are frequently discussed on enthusiast sites such as The Gear Page, Gearspace, and Reverb alongside other small-batch fuzz and vibe makers.

MJM has 16 products cataloged on Equipboard, including Fuzz Effects Pedals, Overdrive Effects Pedals, and Univibe & Rotary Effects Pedals. Their gear is featured by 2 artists, with the strongest followings in Rock. Notable users include Marc Ford and Andrew Watt.