HEDORAH
Spawned from pollution, this creature proved to be one of GODZILLA's most vile foes

HERO ZERO
While possessing the power to turn into a giant superhero, a teenager ran afoul of GODZILLA, and failing to stop the monster, swore off his powers

ICE BOARERSNEW!

INAGOSNEW!
This giant locust is one of the legendary "Disaster Monsters," alongside SORAN and GODZILLA VI
First Appearance: GODZILLA, KING OF THE MONSTERS SPECIAL #1 (Dark Horse comic)

JET JAGUAR
When the Seatopians attack the surface world, JET JAGUAR reprograms itself to combat the invaders' forces, alongside GODZILLA
First Appearance: GODZILLA VS. MEGALON (Toho movie)

JURAH (ZONE FIGHTER)

KAMEBA

KING COBRANEW!

KING KONG
First Appearance (In GODZILLA Universe): KING KONG VS. GODZILLA

KING SEESAR
First Appearance: GODZILLA VS. MECHAGODZILLA (Toho movie)

KOMODITHRAXNEW!

KROLLAR (MARVEL)

LEPIRAX

LEVIATHAN WATCHDOGS (TS)

LITTLE GODZILLA
First Appearance: GODZILLA VS. SPACE GODZILLA (Toho movie)

LORD HOWE MONSTERNEW!

MAGMA
First Appearance: GORATH (Toho movie)

MAGNETIC MONSTERNEW!
First Appearance: GODZILLA: "THE MAGNETIC MONSTER (Hanna-Barbera cartoon)

MAJIN TUOL
This statue of an ancient deity came alive to aid GODZILLA against GHIDORAH, GIGAN and MEGALON in an aborted script

MANDA
First Appearance: ATRAGON (Toho movie)

MANDA IINEW!

MANTA RAY (TS)

MECHAGODZILLA I
First Appearance: GODZILLA VS. MECHAGODZILLA (Toho movie)

MECHAGODZILLA II
First Appearance: GODZILLA VS. MECHAGODZILLA II (Toho movie)

MECHA KING GHIDORAH
First Appearance: GODZILLA VS. KING GHIDORAH (Toho movie)

MECHANIKONG
First Appearance: KING KONG ESCAPES (Toho movie)

MEDUSANEW!

MEGAGUIRUS
First Appearance: GODZILLA VS. MEGAGUIRUS (Toho movie)

MEGALON
First Appearance: GODZILLA VS. MEGALON (Toho movie)

MEGALON IINEW!
As far as is noted, MEGALON II has no relation to MEGALON I other than by name.

MEGANURON

MEGAPEDENEW!

MEGAVOLT MONSTERNEW!
FIRST APPEARANCE: GODZILLA: "THE MEGAVOLT MONSTER" (Hanna-Barbera cartoon)

MIMICNEW!

MINYA
First Appearance: SON OF GODZILLA (Toho movie)

M.O.G.E.R.A.
First Appearance: GODZILLA VS. SPACE GODZILLA (Toho movie)

MOGUERA
First Appearance: THE MYSTERIANS (Toho movie)

MOON MONSTERNEW!
FIRST APPEARANCE: GODZILLA: "MOONLODE" (Hanna-Barbera cartoon)

MOTHRA (larvae)
First Appearance: MOTHRA (Toho movie)

MOTHRA (adult)
First Appearance: MOTHRA (Toho movie)