How to Defeat Phantom Ganon in The Legend of Zelda: Ocarina of Time

Go into the middle of the arena to start the battle.

In the first part of the battle, Phantom Ganon will go into one of the six paintings in the arena, and two replicas of him will come out of two paintings. The real one is lighter than the fake one, and a purple vortex will appear as it comes out. Hit this one with an arrow. You can also use the Hookshot, but this is slower than using arrows. Should you not hit him fast enough, go to one of the Triforce images at each corner of the platform to avoid his electric ball attack, which he hits the center of the arena with.

After doing this three times, he'll get off his horse and attack you with an energy ball. Use your sword to hit the energy ball back. He'll hit it back; repeat this process until he's hit with his energy ball. You can also use an empty bottle to hit the energy ball back.

Once he's stunned, slash him with your sword until he gets back up. When you've damaged him a few times, he'll sometimes do another attack where he charges at you. Avoid this attack, as it does three hearts of damage. You'll know when he's going to do the attack when he twirls his staff around a few times and lets off small magic sparks with it.