For over 60 years, one of cinema's most recognizable icons has been a hulking, reptilian behemoth known as Godzilla -- or Gojira, in his home country. This unlikely star that emerged from the depths of the ocean to level Japanese and U.S. cities was born out of very specific circumstances in war-torn Japan. In the run-up to his theatrical debut, the country was occupied by U.S. and allied forces, who quashed any reporting on the atomic fallout for fear of resistance to the occupation effort. According to Charlotte Eubanks, Assistant Professor of Comparative Literature and Japanese at Pennsylvania State University, all of that changed when a Japanese fishing vessel was caught in the aftermath of a U.S. nuclear test. "When this hit the newspapers, it ignited an enormous scare, as people throughout the country feared that they had been exposed to nuclear radiation through consuming tainted fish.

"That was in March 1954, shortly before the release of Gojira, the opening scene of which features a fishing crew exposed to an unexplained, destructive flash of light." The idea of contaminated survivors of nuclear events walking amongst the population sparked an entire genre in Japanese cinema known as "Hibakusha," though none have cast quite as looming a shadow as Godzilla. With over 30 Japanese and American movies to his name, the atomic kaiju has often had to share the screen to secure his legacy as King of Monsters. You don't become the best without beating the best, and everyone from aliens, to robots to giant spinning turtles have had a crack at the title -- some with a lot more success than others.

15 MEGALON

In Godzilla vs. Megalon, a weird, underground cult -- and by "underground," we mean that literally -- are going about their eccentric lives as normal when top-side destruction starts to get on their nerves. So, they do what anyone in their situation would do: sic a giant beetle with drills for hands on everyone above. And for a while, he seems unstoppable.

Even Jet Jaguar is powerless against Megalon -- and he has his own theme song! Luckily, Godzilla comes to the giant robot's aid, and, despite the bug's superior burrowing skills, lightning horn and ability to puke up napalm hairballs (ugh...) the pair flying-kick the stuffing out of Megalon, a move the filmmakers were so (rightfully) proud of, they played it twice.

14 RODAN

This huge, bipedal pterodactyl was the star of his own 1956 movie before he joined Toho's Godzilla series in 1964's Ghidorah, the Three-Headed Monster. Since then, he's been an on/off ally to the big G. He's also one of many flying beasts in the franchise, able to cause sonic booms with his speed and flap his wings fast enough to produce powerful winds.

Not only has he withstood King Ghidorah's gravity beam, but he's one of only a few Godzilla opponents with some immunity to his signature atomic breath. His cool design (it's hard to beat a dino-adjacent creature) has made him a mainstay in the franchise, though he took a fatal beating from Mechagodzilla in Godzilla vs. Mechagodzilla II.

13 KING KONG

Japan had a big reptile. America had a big gorilla. It was only a matter of time before the two duked it out; a time which finally arrived in 1962's King Kong vs. Godzilla. Now, King Kong may be giant for a gorilla but he had to undergo a considerable growth spurt for his match against Godzilla to even appear plausibly even.

Thanks to a bizarre Frankenstein's monster moment, Kong also gained temporary electrical powers against his aquatic enemy. King Kong's name being first in the title kind of spoils the results of their crossover battle, the validity of which was undermined for years by a now-debunked rumor that there were actually two endings with different victors. Their rematch date is set for 2020.

12 ANGUIRUS

Godzilla has made nice with a lot of other giant monsters over the years to survive, but no partnership has been as enduring as the one he forged with Anguirus. After duking it out against the plucky armadillo/crocodile hybrid in Godzilla Raids Again, the pair became roomies on Monster Island in Godzilla vs. Gigan.

Godzilla even sends Anguirus to investigate some peculiar roars, like a master ordering a dog to pick up a scent, and Anguirus is one of the first to realize that something is impersonating his real BFF in Godzilla vs. Mechagodzilla. Though he lacks any special powers, Anguirus' loyalty and hardiness means he always keeps going, regardless of the odds.

11 M.U.T.O

After 1998's inferior effort, the 2014 reboot of the U.S's Godzilla franchise needed to deliver the monstrous goods -- and most would agree that it did. Amidst an arguable lack of the titular monster himself, the pair of parasitic M.U.T.Os ("Massive Unidentified Terrestrial Organisms") did their villainous duty in wreaking havoc around the world.

The flying couple rivalled Godzilla in scale, dined out on radiation and could emit electromagnetic pulses with a far-reaching radius. There was also the small problem of them trying to start a family together. Humanity needed a champion, and with a direct blast down the throat, Godzilla became our terrifying saviour.

10 MOTHRA

Considering her fame, you'd think that Mothra would have scored way more victories than she has. Though she may have been dubbed "Queen of Monsters" by Toho, she's usually on the defence more than the attack, making her a strong and frequent wing-woman of the King of Monsters. Other than her reflective wings, she's also known for her psychic prowess.

This unique ability allows her to speak to humans, who view her as a divine, phoenix-like being, representing the light of Earth in opposition to Battra -- her sworn enemy's -- darkness. Like a phoenix, Mothra's larva production means she can always come back, even if not quite in her original form.

9 BIOLLANTE

She's beauty and she's grace, she's... got a head stuffed full of teeth! Biollante might never win any Miss America pageants, but what she lacks in conventional human beauty standards, she makes up for by being one of the scariest monsters ever dreamed up by Toho. If Poison Ivy, Swamp Thing and the Alien from Alien had a baby, it would be Biollante.

In Godzilla vs. Biollante, she's actually the result of DNA splicing using material from a mutant rose, a human and Godzilla himself. She has a couple of different forms, eventually evolving into her final "Rose" one, complete with attacking vines and a beaked mouth filled with hundreds of fangs. Her regeneration ability also gave Godzilla some trouble.

8 HEDORAH

The message at the center of the entire Godzilla franchise is that humanity is the greatest threat to Earth. Hedorah is the least subtle incarnation of that warning, and probably wouldn't look out of place if he appeared in an early environmental-themed episode of Mighty Morphin' Power Rangers. His name comes from the Japanese word for mud and suitably, he's just a big, toxic, oozing lump.

In Godzilla vs. Hedorah, he mutates from a squid-like thing to a flying saucer to a reptilian, humanoid form and, with his metallic outer body and slanted, red eyes, looks grossly intimidating in any shape. His pollutant excretion is his greatest weapon, though -- potent enough to melt people down to skeletons.

7 GIGAN

With his visor-shaped eye and green coloring, Gigan looks like Boba Fett designed by H.R Giger. Though it's hard to tell with the fins and beak, his exact species is "Cybernetic Space Dinosaur," so basically all of your childhood fantasies come to life. The cybernetic parts are visible in his giant, scythe hands and rotating chest blade.

Despite being defeated embarrassingly easily by Godzilla in Godzilla: Final Wars, Gigan's ruthless attitude has made him a fan favorite, perhaps because weaponry of any kind is rare in the franchise. As if he didn't look scary enough, his modified form swapped his scythes for chainsaws. (He could easily find work today in the next Nightmare on Elm Street film.)

6 ORGA

Godzilla's DNA gets around a lot, and Orga is one of the many huge abominations his genetic gunk has helped create. Introduced in Godzilla 2000: Millennium -- the first in the Millennium era of Godzilla movies -- Orga began life as a group of aliens who crash-landed on Earth, and eventually merged with Godzilla's genes as well as each other.

Orga sought to replace the G-man, fending off his atomic blasts with its super fast regeneration and wave motion cannon. Like the original Superman, the mutated alien could also leap tall buildings in a single bound. Despite that goofy skill, the Godzilla pretender actually got close to beating the original by unhooking its jaw and trying to swallow him whole.

5 MONSTER X

Anything with "X" in its name instantly sounds cool, and Monster X doesn't just sound cool -- he is pretty cool. This is partly thanks to his heritage as one of King Ghidorah's species, and partly because he's essentially a massive dinosaur-like creature with an armored shell, skulls for shoulder pads, a spiked head and red eyes.

In Godzilla: Final Wars, he not only flings Godzilla around Tokyo with frightening ease, he seems to have a great time while doing it. Though he's initially mind-controlled into battling Godzilla by evil aliens, he continues brawling even after that control has been cut, and takes a point-blank atomic blast from his enemy like it's nothing.

4 SPACEGODZILLA

Of all the copycat monsters, SpaceGodzilla is one of the closest-looking clones of the franchise's main star. He's just a cosmic version of Godzilla, complete with giant, crystals sticking out of his back for... space reasons. SpaceGodzilla may sound and seem silly -- and he is -- but he's guilty of one of the most heinous acts in Godzilla history!

He takes Godzilla's son! As well as imprisoning Baby Godzilla (also known as Minilla), he cruelly assaults the little guy, and quickly kicks the scales off of Godzilla Sr. with his mighty Corona beam, which he can somehow control as it travels through the air. Godzilla had to enlist the giant mech, M.O.G.E.R.A's help to beat him.

3 MECHAGODZILLA

Mechagodzilla is so iconic in the Godzilla pantheon, the two even faced off outside of their franchise in Steven Spielberg's Ready Player One. As it says on the tin, he's a robo-version of Godzilla; so well-designed, in fact, that he was able to effectively disguise himself as his namesake in Godzilla vs. Mechgodzilla.

Mechagodzilla also earned himself a proper sequel, appropriately titled Godzilla vs. Mechagodzilla II, cementing himself as one of the kaiju's fiercest adversaries. It normally takes quite a few other monsters working together to take him down. Thank Godzilla he's on our side in the Millennium series, taking a heroic role as mankind's mecha guardian.

2 DESTROYAH

In his final form, Destroyah really looks like he means business, and his business is very mean. He's another Godzilla-based monster, with added spikes, facial horns, a tail pincer and huge, demonic wings. But his devilish appearance isn't the most evil thing about him. Destroyah is one of Godzilla's greatest foes because he was spawned from Godzilla's first defeat.

In the original 1954 movie, Godzilla was taken down by the Oxygen Destroyer, a device that ended up transforming the bipedal crustacean in Godzilla vs. Destroyah into a living weapon. With this huge advantage, Destroyah faces arguably the strongest version of Godzilla at the time, and nearly finishes him off for good.

1 KING GHIDORAH

If the entire Godzilla franchise was boiled down into a single video game, King Ghidorah would be the final boss. Of the dozens of wacky and powerful monsters that the Doctor Pepper-chugging reptile has fly-kicked and boxed his way through, King Ghidorah is without a doubt his most bitter rival. Debuting in 1964's Ghidorah, the Three-Headed Monster, he's also one of Godzilla's most frequent co-stars.

As well as his incredible durability, King Ghidorah's signature attack is his gravity beam -- a golden stream of energy that he fires from his mouth like a fire-breathing dragon that rivals Godzilla's atomic breath in strength. Strap yourself in for a royal rumble between these two in 2019's Godzilla: King of the Monsters!