Mad Ferret
Madge
Madmeano
Mandrake Root
Mandrake Swamp
Marble Garden Zone
Marble Zone
Marcel Skunk
Mark and Sparks
The Marxio Brothers
Masher Badnik
The Master Emerald
The Master Sentinel
Robotnik's Matter Transporter Monitor
Matthew Corgi
Maude and Harold Mudd
Max Gamble
Max Gamble's Metal Mate
Max Gamble's Mob
Mecha Amy
Mecha Johnny
Mecha Lizard
Mecha Metallix
Mecha Sonic
Medusa
Meek Tribe
Robotnik's Mega Crusher Matic
Mega Glue
Mega Mack
Megapolis City
Megatox
Mekanik
Mello
Mephistor
Mephistor's Boys
Planet Meridian
Mesmer
Metallix
Metamoto
Metamorphia
Metropolis City Bank
Metropolis High Security Prison
The Metropolis City Zone
Mighty The Armadillo
Miles "Tails" Prower
The Mind Root
The Mini-Speed Treadmill
The Minotaur
The Miracle Planet
The Mirror Prison
The Mirror Zone
The Misery Zone
Mister Fry
Mister Shifter
The Mobian Channel
Mobius 5000
Planet Mobius
Mobius "b"
Mobius Rings
Mootant Village
Morain Blackthorn
Castle Morbidden
Motobug Badnik
Motobotnik
Morton
The Mountain Of Destiny
Ms. Alpha, Mr. Gamma, Mr. Delta and Mr. Beta
Tekno's Multi-Image Creator
The Mummy Boys Of Aggro
Muscleman
Mushroom Hill Zone
Mushroom Valley
Mystic Cave Zone
The Mystic Genies
Lord Sidewinder's Mystic Palace
The Mysterious Traveller