The Slim Phatty is a monophonic analog synthesizer manufactured by Moog Music from 2011–2014. It is considered to be an entry-level synthesizer in the Moog family. Its design is based on the Little Phatty, which in turn is a more modernized version of the Minimoog Voyager. It is among the first synthesizers created and produced following the death of Moog founder Robert Moog in 2005. The Slim Phatty is also the first Moog (beside the Little Phatty) that is capable of USB connectivity. It was inferred that Moog would be releasing a new and possibly more stripped down synthesizer when reports surfaced that Moog had registered a trademark for the name "Slim Phatty".

The Slim Phatty is able to make use of MIDI controller integration via out, in, and "thru" channels. The only other Moog synthesizers that can boast this capability are the Little Phatty, Minimoog Voyager, and the early Memorymoog+. It also features two robust oscillators, diverse tuning controls, and the patented “Moog Ladder” filters. Also included are a large number of patches or preset sound settings. Unlike many synthesizers, it does not possess a keyboard, so a MIDI or other sound input is required in order to create sound to modulate or filter. It is also small in size, and weighing in at roughly 5.5 lbs. For these reasons, the Slim Phatty is useful in both studio recording and live playing.