Groudon (Ground-type)
* Found in the Cave of Origin after defeating the Elite Four and becoming Champion.
* Can only be captured after obtaining the Red Orb.
Kyogre (Water-type)
* Found in the Cave of Origin after defeating the Elite Four and becoming Champion.
* Can only be captured after obtaining the Blue Orb.
Rayquaza (Dragon/Flying-type)
* Found in the Sky Pillar after Groudon and Kyogre are defeated.
* Can only be captured after obtaining the Red Orb and Blue Orb.
Regirock (Rock-type)
* Found in the ancient temple in the desert, accessible after obtaining the three Regi keys.
* You need to activate the temple by using the keys in a specific order.
Regice (Ice-type)
* Found in the ancient temple in the desert, accessible after obtaining the three Regi keys.
* You need to activate the temple by using the keys in a specific order.
Registeel (Steel-type)
* Found in the ancient temple in the desert, accessible after obtaining the three Regi keys.
* You need to activate the temple by using the keys in a specific order.
Latias (Dragon/Psychic-type)
* Found in the Southern Island after obtaining the Eon Flute.
* Only available after obtaining the Eon Flute.
Latios (Dragon/Psychic-type)
* Found in the Southern Island after obtaining the Eon Flute.
* Only available after obtaining the Eon Flute.
Jirachi (Steel/Psychic-type)
* Found in the Wishmaker's House after obtaining the Star Stone.
* This is a rare encounter, and you will need to use the Star Stone to wake it up.
Mew (Psychic-type)
* Not technically obtainable through normal gameplay. Requires a glitch or cheat device to acquire.
Note: While you can technically obtain Mewtwo in Pokémon Emerald, it is not a Legendary encounter. It can be found in the abandoned Pokémon Mansion in the Slateport City area.