It's catchable in Red/Blue/Yellow, FireRed/LeafGreen, HeartGold/SoulSilver, and X/Y. You catch it in the Cerulean Cave in Cerulean City in Red/Blue/Yellow, FireRed/LeafGreen, and SoulSilver, and the Unknown Dungeon in the Pokemon Village in X/Y.
Mew and Mewtwo are not found anywhere in the Sinnoh region.
mystery gift
You cannot catch Mew in "Pokémon Ruby."or you can get mew-two in fire red or leaf green.
I don't think you can catch MEW without a action replay. But you can catch MEW2 in Pokemon Fire Red or Leaf Green. You CAN'T cach mew without an action replay, but you can trade mew-two from the other games to the newer ones
in Pokemon yellow, blue, red, fire red, and leaf green you can find mew-two in cerulean cave after you have beten the game, but for mew at the moment you can not get it without cheats...
At the crulian cave
You don't
You have to beat the elite four and then go to cerulean cave and then you go all the way through then at the end is mew two and you have to catch it that is it
you cant unless its an event or a action replay code or you can not catch mew or two mews
cheat
Mt.Moon
The Cerulean Cave