King Dodongo

Infernal Dinosaur: King Dodongo makes its gaming debut in Ocarina of Time. He is the second boss the player must face and defeat in order to obtain the Spiritual Stone, Goron's Ruby, from the Goron leader known as Darunia.

You fight him in a room with a lava pit in the middle. Avoid this at all costs. King Dodongo will attack in one of two ways. He will suck in a massive amount of air to blow out fire, or he will roll into a ball and attempt to run Link over.

While he is sucking in air, take out a bomb (acquired inside the dungeon) or grab a bomb flower from nearby. Throw the bomb right into his mouth. It will explode inside him, causing him to momentarily faint. Use this opportunity to take out your sword and slash him in the face. He will then rear up, roll into a ball, and try to run you over. In order to avoid this, you can stand on the small slope between the lava and the arena. None of Dodongo's attack will hurt you there. When he hits the wall at the other end of the arena, he will unfold and repeat the process. Bomb him and slash him four times to kill him. When he is dying he will curl into a ball for the last time and roll into the lava pit, frying himself to a crisp. Link is rewarded with a Heart Container and the Spiritual Stone from a very pleased Darunia.

Four Swords Adventures
King Dodongo makes another appearance in The Legend of Zelda: Four Swords Adventures, where he has a similar appearance and is defeated using a similar strategy (by tossing a level 2 bomb into his maw when he is about to breathe fire, which must be repeated three times.)

Trivia
There is a simpler way to avoid King Dodongo's rolling attack if you feel daring: equip the Hylian Shield (if you have one) and, standing right in the monster's path, raise your defenses. You will be safe, and the Infernal Dinosaur will surprisingly bounce harmlessly off your shield in a shower of sparks while continuing his circuit around the room.