{{Infobox Film
|作品名=三大怪獣 地球最大の決戦
|原題=Ghidorah, the Three-Headed Monster
|監督=本多猪四郎
|製作総指揮=清水雅
|製作=田中友幸
|脚本=関沢新一
|出演者=夏木陽介<br />星由里子<br />若林映子<br />小泉博<br />ザ・ピーナッツ<br />伊藤久哉<br />沢村いき雄<br />平田昭彦<br />志村喬
|音楽=伊福部昭
|主題歌=
|撮影監督=
|撮影=小泉一
|編集=藤井良平
|配給=東宝
|公開=1964年12月20日（日本）
|上映時間=
|製作国=
|言語=日本語
|制作費=
|興行収入=
|前作=モスラ対ゴジラ
|次作=怪獣大戦争
|allcinema_id=
|kinejun_id=
|amg_id=
|imdb_id=
}}
『'''三大怪獣 地球最大の決戦'''』（さんだいかいじゅう ちきゅうさいだいのけっせん）は1964年に公開された日本映画で、ゴジラシリーズの第5作である。1964年12月20日公開。観客動員数は541万人。併映は『花のお江戸の無責任』。

後に『'''ゴジラ・モスラ・キングギドラ 地球最大の決戦'''』と改題され、1971年冬の東宝チャンピオンまつりでもリバイバル上映された。

== 概要 ==
シリーズ最大の悪とされているキングギドラが誕生した作品であり、キングギドラの破壊性に最も富んだ作品とされている。

タイトルの「三大怪獣」とは地球の三大怪獣ゴジラ・ラドン・モスラのことを指している。

本作のストーリーは『ローマの休日』から強く影響を受けている。プロットは平井和正作『幻魔大戦』に強い影響を与えている（冒頭の飛行機のシーンや、予言者の呼びかけなど）。

『空の大怪獣ラドン』と『モスラ対ゴジラ』の直接的な続編にあたる。

ゴジラが正義の側になった（但し、モスラのように完全な“人間の味方”ではない）、つまりこれ以前の姿から離れる事になった作品である。常に“人類の脅威”としての存在だったゴジラが善に変わった為か、一部のファンにはこれ以降の昭和シリーズを毛嫌いする傾向があるようだ。

本作におけるゴジラの熱線は、海上のシーンを除いて全て霧状に表現されている。

== ストーリー ==
異常気象に見舞われた地球。流星群が地球に飛来し一つの巨大なラドンが復活すると予言する。また、出港しようとする船に出港中止を求めて、暗にゴジラの出現を予言する。

それらの予言は誰も信じないが、進藤は彼女が死亡したはずのサルノ王女と確信、単独で捜査を開始する。また、その頃日本に来ていた小美人たちは、金星人の予言を信じて船に乗るのを避ける。そして進藤の妹の直子は金星人と名乗る女性を保護して横浜市内のホテルに宿泊した。だが、セルジナから来た、王女暗殺を企てる一味も彼女がサルノ王女と見抜き、直子らの宿泊するホテルを襲撃した。そこへ、彼女の予言通り阿蘇山から出現したラドンと、船を襲って海から現われたゴジラが横浜に上陸して戦いを始め、小美人たちの機転もあって暗殺者たちの計画は失敗する。

{{Infobox_Film
|name            =Ghidorah, the Three-Headed Monster
|image           =Ghidorah the Three-Headed Monster 1965.jpg
|director        =Ishirô Honda
|producer        =Tomoyuki Tanaka
|writer          =Shinichi Sekizawa
|starring        =Yosuke Natsuki<br>Yuriko Hoshi<br>Hiroshi Koizumi<br>Akiko Wakabayashi
|music           =Akira Ifukube <br> Song  music by Hiroshi Miyagawa (called "Yasushi Miyagawa" in US credits; a common mistranslation), words by Tokiko Iwatani
|cinematography  =Hajime Koizumi
|distributor     =Toho <br> Continental Distributing (USA)
|debuts          =King Ghidorah
|released        =December 20, 1964 (Japan) <br> September 13, 1965 (USA)
|runtime         =92 min.
|language        =Japanese
|budget          =
|imdb_id         =0058544
|preceded_by = ''Mothra vs. Godzilla''
|followed_by = ''Invasion of Astro-Monster''
|}}

'''''Ghidorah, the Three-Headed Monster''''', released in Japan as  and originally released in the US as '''''Ghidrah, the Three-Headed Monster''''', is a 1964 tokusatsu kaiju film, and is the 5th film in Toho's Godzilla series.  It was directed by Ishiro Honda with special effects by Eiji Tsuburaya.

This movie is noted for having Godzilla playing a role where he benefits Japan, instead of trying to destroy it.  It also features Mothra and Rodan, and introduces King Ghidorah, a very Chinese-looking space dragon, perhaps representative of Japan's anxieties surrounding China's satellite weapon program at the time.

==Plot==

In 1964, a princess from Selgina, a small Himalayan country becomes possessed by the spirit of a Venusian and escapes a plane just as it explodes. As this happens a meteorite falls from the sky containing King Ghidorah, the monster responsible for her planet's destruction. At the same time, Godzilla and Rodan emerge from hibernation and not only attack Japan, but each other as well. Mothra, along with her twin priestesses, attempt to convince Godzilla and Rodan to stop fighting each other and to team up to fight the three-headed monster. At the same time, the princess is being hunted by a group of assassins who want to kill her so that her enemies can take over her homeland.
Then, just when the only living assassin is about to kill the princess, King Ghidorah crushes him by knocking over a pile of boulders on him. Godzilla, Rodan, and Mothra finally drive King Ghidorah off. The movie ends with the princess going back to her home land and Godzilla and Rodan watching Mothra swim back to Infant Island.                                           

==Trivia==

* Because the completion of Akahige by director Akira Kurosawa was falling behind, this film was pushed through to cover the planned release of Akahige. Therefore, this new Godzilla film was released successively in the winter, proceeded by  ''Mothra vs. Godzilla'' in spring of the same year.

* Princess name 『MAASU-DOORINA-SARUNO』is a parody of the meaning "Oh, do you pass by my front?" in Japanese. 

* The Yokohama Marine Tower, a miniature of which is destroyed by King Ghidorah's rays in the film, was completed three years before the movie was produced.

* The Godzilla suit design used in this movie is referred to as “Sandai-Goji.” 

* Godzilla not once uses his atomic breath against Ghidorah despite the original Japanese Poster showing that he does.

* An early concept for Ghidorah had him with rainbow-colored wings and his three heads spitting fire from their mouths, instead of gravity beams which was used in the final draft.

* The first Godzilla film to not feature military weapons such as tanks and jets, used against the monsters, and was the rigor-du-jour in previous films.

* In the game ''Ed, Edd n Eddy: The Mis-Edventures'', the Ravenge of Ed-Zilla bonus level, The "Kankerator" (the Kankers as a monster) is based on Ghidorah.

*This film marks the first appearance of Rodan in a Godzilla film.

*  In the conversation with Mothra, Godzilla states that he only hates humans because humans hate him, and because of what he perceives as unprovoked attacks towards him,  suggesting that he was not really a villain in the first place. 

*This film also marks the first appearance of Invasion of the Astro Monster, Destroy All Monsters, Godzilla vs. Gigan, Godzilla vs. King Ghidorah, GMK, and as Godzilla's final opponent dubbed as Kaiser Ghidorah in Godzilla: Final Wars.   

*In Mothra Vs. Godzilla, two Mothra larva hatched but in this movie there is only one. This is explained in this film, via exposition by the twin faeries, or Shobijin (Little Beauties), stating that one of the twin larva had expired.

*A multitude of deleted scenes were exised from the original Japanese print and are widely unavailable for viewing. These include:
-A continued conversation between Shindo and Detective Okida after Shindo sees her picture for the first time. He marvels at her beauty, but then Okida scolds him for being distracted from his mission.
-More dialogue between Malness and his gang.
-Longer conversations held in Dr. Tsukamoto's laboratory.
-A hurricane wind duel between Rodan and King Ghidorah, which results in Rodan being blasted backwards by an exceptionally powerful gust.
-A brief shot of Godzilla biting down onto one of Ghidorah's necks.
-A shot of Ghidorah angrily throwing all three other monsters off him at once.
-A spectacular matte shot of Ghidorah chasing victims during his attack on Yokohama. This was cut at the whim of director Ishiro Honda, which is unfortunate because the shot was one of the most expensive in the movie.

==U.S. release==
The English-dubbed version was presented in American theaters in September 1965 by Walter Reade-Sterling, and distributed by Continental Distributing on a double bill with Elvis Presley's musical-comedy, ''Harum Scarum''. Originally titled ''Ghidrah, the Three-Headed Monster.''

Several alterations were made to the American version, including:

* Much of Akira Ifukube's score was cut.

* Ghidorah's name was romanized as "Ghidrah".

* The line "Are you a man or a woman?" It would be easier if you removed your clothes!" became, "Are you a boy or a girl? Why don't you do a striptease for us!"

* In the American version, King Ghidorah destroys Mars (it was Venus in the Japanese version), and the Princess claims that she is from Mars. This was most likely because of the strong association the western world has with the possibility of Mars having been able to support life.

* Continuity Error: The sequence of Godzilla climbing on the docks in Yokohama harbor was changed around. First he is on the docks, then appears to be back in the bay, and then back on shore.