What are all the legendary Pokemon for LeafGreen?

Answer 1

There are seven legendary Pokemon in Leaf Green, however you only have access to five of these.

Mewtwo, Level 70, Psychic type: Obtained in Cerulean Cave after beating Elite Four and fixing the machine that allows trade between Ruby and Sapphire.

Articuno, level 50, Ice/Flying: Obtained in Sea Foam Islands after solving the boulder puzzle in the cave.

Zapdos, Level 50, Electric/Flying: Obtained at the end of the Power Plant. Go to the northern entrance of the Rock Tunnel, go north and Surf on the water all the way around to get to it.

Moltres, Level 50, Fire/Flying: This can be obtained at the top of the mountain northeast of the first Island.

These are for the first 150 Kanto Pokedex

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The next three you can only get one of, and appear in random grassy patches around the Kanto region. The one that you can find is relevant to the starter Pokemon you chose, and only appear when your pokedex is upgraded (and I think after you beat the new and improved Pokemon Elite Four)

If you chose Bulbasaur, Entei will be there

If you chose Squirtle, Raikou will be there

If you chose Charmander, Suicune will be there

Hopefully that answers your question on all the Legendary Pokemon for Leaf Green.