Forest Temple Boss - Odolwa

Snow Temple Boss - Gogt

Water Temple Boss - Gygorg

Stone Temple Boss - Twin-Mold

Final Battle Boss - Majora's Mask (3 transformations)

Odolwa - is easy, keep him Z-targeted, and hit him with an arrow whenever he lets down his guard. You can block all his attacks except for his big swipe, which you can role under. When he calls bugs, blow ‘em up. Note: you can kill him faster with bomb flowers which are around the battleground.

Gogt - I'd say he is one of the easiest boss through out the game and one of the funiest too. There isn't much to beating this boss but it can be tough. Unfreeze him with a fire arrow and then he will start to run around the track that you are standing on. Roll up and follow him. Get your speed up so that your spikes come out and try to keep hitting him from behind. He has a number of ways to prevent you from doing this. He kicks up rocks that will slow you down, stalactites will fall from the ceiling and get in your way, he will throw bombs at you, and if he can get far enough ahead, he will shoot you with an electric ball. When you magic gets low, there are green jars on the course to replenish with. Keep chasing and hitting him until he dies.

Gygorg - The toughest boss throughout the game in my opinion. You use Zora Link to fight him. He swollows you up like a chewing gum and spit you out with 11/2 heart lost. He is extremely powerful. Easiest way to beat him is to stay to his side and NOT in front of him (Don't let him see you). This guy is a pain, but only takes a few shots to kill. He will try and get you in the water with him so he can eat you. He will jump out of the water and try to ram you off the platform. If he can see you on the edge, he will ram the platform to knock you into the water. The only real advise I can give is to stay in the middle if you see him getting ready to ram. Try to find and target him. Shoot him with an arrow. He will be stunned. Put on the Zora Mask and swim to him fast before he shakes it off. Use your shock shield to damage him. Then get back to the platform with all due haste. Repeat this until he dies. After three hits, he will release smaller fish that give you hearts when you kill them. Two more hits after that should finish him off. He's tough if you don't time things right. It took me some practice so hang in there.  

Twin-Mold - Enter the boss room and drop down the hole. Put on the Giant's Mask and attack the two worms by hitting them in the head or tail. The Giant's Mask uses magic power. You can get magic bottles by hitting the stone columns around the dessert with your sword. Take the Giant's Mask off and get the bottles when you need them. It's pretty straight forward. Keep hitting them until they are dead. TIP: If you buy some Chateau Romani then you have unlimited magic power until time is reset.