Reunited as adults, Wawa (Marie Wawa) and Dain (Mungau Dain) explore forbidden love in “Tanna.” (Philippe Penel/Lightyear Entertainment)

There’s something thrilling about a movie that introduces us to a corner of the world we never knew existed. “Tanna” is that kind of film. It was shot on the remote South Pacific island that gives the movie its name with a cast composed entirely of local nonactors. The people of Yakel village live off the land, ignoring the modern world while adhering to a set of traditional rules known as the Kastom.

The Kastom is, in some ways, the tribe’s salvation, but it may also spell its doom, thanks to a couple of star-crossed lovers. The story sounds a lot like “Romeo and Juliet,” but it’s based on real events.

We are introduced to this world through a rebellious little girl named Selin (Marceline Rofit), who watches as her older sister Wawa (Marie Wawa) falls in love with Dain (Mungau Dain), the grandson of the tribe’s chief. In their culture, marriage is not a union of love, but a strategic alliance, and Wawa is betrothed to a man in another warring tribe. That marriage is supposed to heal old wounds, uniting the antagonists in peace after years of violent feuding. Of course, Wawa and Dain have other ideas.

That rather simple tale unfolds against a stunning backdrop. The island of Tanna is about as untouched as you can imagine. Wawa and Dain, who had been childhood friends before he left their village for parts unknown, first reunite in a forest amid ferns, palms and other lush foliage, and their instantaneous love only seems more predestined in this Shangri-La.

The tribe’s people also make frequent trips to the island’s active volcano, which adds a mystical element to the movie. In one striking scene, Selin and her grandfather ascend the mountain at dusk — shadowy figures walking in front of a burst of smoke, ash and embers.

The movie’s Australian directors, Martin Butler and Bentley Dean, who wrote the script with John Collee, have an attention to earthly detail that gives the movie a beauty to rival a nature documentary. But they also have a keen anthropological eye. The pair spent seven months with the tribe, getting to know its members and their traditions and rituals, which are seamlessly integrated into the plot, educating the viewer without making the tribe’s experience seem overly exotic.

At times, the movie appears to favor the careful study of Yakel’s culture over the emotion of the story, which takes some of the wallop out of the climax. Even so, the movie is a tremendous accomplishment, especially considering that the cast had never seen cameras before — much less movies — yet still agreed to star in the drama. Their performances are as stunning as the setting, and that’s truly saying something.

Unrated. At Landmark’s E Street Cinema. Contains nudity. In Nauvhal with subtitles. 104 minutes.