A 1985 film directed by Creator/JohnBoorman and starring Creator/PowersBoothe, VeryLooselyBasedOnATrueStory.

Bill's son is kidnapped by an Amazon tribe. Bill tried to pursue but lost them in the jungle. Over a decade later, he tries to arrange an expedition to find his son. The results are a disaster. His partner is eaten by cannibals and he flees only to find his son as one of the natives trying to kill him.

Tommy, now a young man, recognizes his father and helps him escape. Tommy takes him to friendly natives who care for Bill. Bill learns of how completely Tommy has transformed into a tribal man speaking their language as if it was native and as if his father's language was foreign. Then the tribe drugs Bill and takes him back to civilization. Bill wakes up with no clue where his son is.

A deadly conflict arises between some of the natives and the ones who ate Bill's partner try to kill Tommy's adopted family. Tommy goes on a quest into the city even though he's a tribesman. He finds his dad and the two of them rescue Tommy's adopted family. Bill helps the tribe further as Tommy returns to the jungle to live.

!! ''The Emerald Forest'' contains examples of:
* TheAmazon: Set where the city clashes with the jungle.
* UsefulNotes/{{Brazil}}: An unknown city, near the Rainforest. Shot in the states of Pará, Rio de Janeiro and São Paulo.
* CannibalTribe: The [[spoiler: Fierce People.]]
* ConLang: The movie has a [[spoiler: fictional tribe, culture and language, based on other Amazon cultures, and on {{Mayincatec}}.]]
* DenOfIniquity: The bar-brothel. Such a bad place that the [[spoiler: BigBad and TheDragon teach the CannibalTribe how to shoot guns there.]]
* GoingNative: Tommy was [[spoiler: raised as a native, but even when he had the chance to return to the city and modern world, he remained a native. Actually, he even becomes the savior and lawful chief of the tribe, first by finding the Sacred stones, then saving the women]].
* GreenAesop: Native people "still know what we have forgotten", as said by the ClosingCredits. The deforestation is bad :
-->'''Invisible man''': They are taking the skin off The World. How will it breathe ?
* ImAHumanitarian: [[spoiler: The Fierce People eat their enemies.]]
* InHarmonyWithNature: The Invisible People, as a {{Foil}} to the "modern" people.
* LanguageBarrier: Downplayed, since both [[spoiler: Bill and Tommy understand a little of each other's language. They still have very different native tongues.]]
* {{Mayincatec}}: Set in modern Latin America, but still valid with [[spoiler: the priests, ceremonial paintings, magic chaman with a drug culture, cannibalism, Sacred stones and the usual jungle with its classic wildlife.]]
* SexSlave: [[spoiler: The Evil {{Mooks}} use the CannibalTribe to kidnap young Amazonian women, who are MadeASlave for this purpose. The climax is about freeing them from their DenOfIniquity.]]