HTTYD 1

The viking village of Clan Berk, located on a remote island, is attacked frequently by Dragons, which take livestock, damage property and endanger lives. Hiccup, the awkward fifteen-year-old son of the village chieftain, Stoick the Vast, is deemed too scrawny and weak to fight the dragons, so he instead creates mechanical devices under his apprenticeship with Gobber, the village blacksmith, though Hiccup's inventions often backfire. During one attack, Hiccup uses a bolas launcher to shoot down a Night Fury, a dangerous and rare dragon of which little is known, but no one believes him, so he searches for the fallen dragon on his own. He finds the dragon in the forest, tangled in his net, but cannot bring himself to kill him, and instead sets him free.

Stoick assembles a fleet to find the dragons' nest, and enters Hiccup in a dragon-fighting class taught by Gobber with the other teenagers, Fishlegs, Snotlout, twins Ruffnut and Tuffnut, and Astrid, a tough Viking girl on whom Hiccup has a crush, to train while he is away. Hiccup returns to the forest and finds the Night Fury still there, trapped in a cove and unable to fly because Hiccup's bolas accidentally tore off half of his tail fin. Hiccup befriends the dragon by offering fish and giving him the name 'Toothless,' after his retractable teeth. Feeling guilty for crippling Toothless, Hiccup designs a harness rig and a prosthetic fin that allows the dragon to fly, but only with Hiccup riding, controlling the prosthetic.

Hiccup learns about dragon behavior as he works with Toothless, and is able to subtly and nonviolently subdue the captive dragons during training, earning him the admiration of his peers but causing Astrid to become increasingly jealous and suspicious of his behavior. Meanwhile, Stoick's fleet arrives home unsuccessful, though Stoick is cheered by Hiccup's unexpected success in dragon training. Hiccup is judged the winner of his training class, and must kill a dragon for his final exam. He tries to run away with Toothless, but Astrid ambushes him in the forest and discovers the dragon. Hiccup takes Astrid for a sunset flight to demonstrate that Toothless is friendly. When Astrid reminds Hiccup of the exam, Toothless unexpectedly takes the pair to the dragons' nest, where they discover a gargantuan dragon named the Red Death. The smaller dragons continuously feed it live food in lieu of being eaten themselves; the two realize that the dragons have been attacking Berk under duress. Astrid wishes to tell the village about their discovery, but Hiccup advises against it to protect Toothless.

Back at the village the next day, Hiccup faces a captive Monstrous Nightmare dragon in his final exam. Instead of killing him, however, he tries to subdue him in an attempt to prove that dragons can be peaceful. When Stoick inadvertently angers the dragon into attacking, Toothless escapes the cove to protect Hiccup, but is captured by the Vikings in the process. Hiccup accidentally reveals to Stoick that Toothless knows the location of the dragons' nest. Stoick disowns his son, and sets off for the nest with Toothless chained to the lead ship as a guide. After the Vikings have left, Hiccup is devastated, but Astrid prompts him to come to the realization that he spared Toothless out of compassion and empathy, not weakness. Hiccup then regains his confidence to go after Toothless and save him along with Astrid and the other teens, and shows them how to befriend the training dragons.

The Viking attackers locate and break open the dragon's nest, causing most of the dragons to fly out, but also awakening the Red Death, which soon overwhelms the Vikings. Hiccup, Astrid, and their fellow pupils fly in, riding Berk's captive training dragons, providing cover fire, and distracting the Red Death while Hiccup frees Toothless. Hiccup almost drowns while doing so, but Stoick saves them both, reconciling with his son. Toothless and Hiccup destroy the Red Death by puncturing its wing membranes and then tricking the beast into making a plunge from which it cannot pull up after shooting a fireball into its mouth. Toothless saves Hiccup from being killed, but Hiccup loses his lower left leg. Hiccup awakens back on Berk, finding that Gobber has fashioned him a prosthesis, and he is now admired by his village including Astrid, who kisses him in front of the village. Berk begins a new era, with humans and dragons living in harmony