There are lots of legendary pokemon!

 

This is Zapdos, Articuno and Moltres. three legendary birds, also known as the Winged Mirages, are the resident legendary trio of the Kanto region. They are Electric Type pokemon, Ice type pokemon and Fire type pokemon.

This is Mew and Mew two. They are not a pokemon that evolved with one body. They are different and seperate pokemon which is a very powerful pokemon.
Mewtwo is revealed to have been cloned from Mew in the journals in the Pokémon Mansion. Unlike most Pokémon, however, Mew gave live birth to Mewtwo, rather than laying an egg and Mewtwo hatching from it. Mewtwo was too powerful, however, and it escapes from the Pokémon Mansion, destroying it in the process. Mewtwo then makes its home in Cerulean Cave, where all kinds of powerful Pokémon live.

This three pokemon has known as Legendary beast. They are Entei, Raikou and Suicune. These legendary beasts, so named because their features are reminiscent of both canine and feline animals, were trapped in the Brass Tower when it was struck by lightning and burned to the ground, resulting in their death. The trio was revived by the power of Ho-Oh, and now roam across the land because of their great power.

This pokemon has known as Lugia and Ho-oh. Lugia and Ho-Oh are a pair of legendary birds which formerly resided in Ecruteak City atop tall towers, leading to their designation. However, when the Brass Tower, home of Lugia, was struck by lightning, it burned to the ground, and both flew away, Lugia to make its new home in the Whirl Islands and Ho-Oh to search the world for a pure-hearted Trainer. The two are thought to be as closely related as they are polar opposites, being based on the eastern legends of the Fènghuáng and Ryūjin.

Although it has no relation to Mew that has been revealed, Celebi was dubbed the "New Mew" when it was introduced in Generation II because of their similar size and stats, as well as the status of being the last in the National Pokédex as of its generation and being unobtainable through normal gameplay. Unlike Mew, however, it was not believed to be the ancestor of all Pokémon, but merely the guardian of forests, traveling through time to make sure of their purity.

They usually called Legendary Golems. They are Regice, Registeel and Regirock. his third trio of legendary Pokémon, based on the golems of Hebrew legend, featured minimally in Hoenn-region legend. Based on the three ancient ages of humanity, the ice age, the stone age, and the iron age, the legendary golems took a back seat among the legendaries introduced in their generation, and are sometimes referred to by fans derisively as the "legendary trash cans". Truly, this legendary trio, as well as its master, Regigigas, feature the most complicated method of in-game availability, with puzzles made of braille in the Hoenn region being the keys to unlocking their mystery.

 Another of Hoenn's minor legendary Pokémon, Latias and Latios do not feature a distinct legend behind them. Nonetheless, they are incredibly rare, with only one of the two available normally to players, and the other available through an event.
Latios and Latias take on counterpart availability in Pokémon Ruby, Sapphire, and Emerald as well as Pokémon HeartGold and SoulSilver, with Latios being a roaming Pokémon in Ruby and SoulSilver, and Latias doing the same in Sapphire and HeartGold. In Emerald, after the player has defeated the Elite Four, their mother will ask if the Pokémon mentioned on TV was red or blue, and depending on that, one of the two will be roaming Hoenn. The other member of the duo will be found on Southern Island, accessible by Eon Ticket, in Ruby, Sapphire, and Emerald, and in Pewter City, through the Enigma Stone event, in HeartGold and SoulSilver.

The trio of super-ancient Pokémon, known for their weather-related abilities as the weather trio, serve as the version mascots of Pokémon Ruby, Sapphire, and Emerald and represent the three major components of the Earth: the hydrosphere, the lithosphere, and the atmosphere. Said to shape the land and sea, respectively, Groudon and Kyogre are among the most powerful legendary Pokémon, while Rayquaza prevents the two from quarreling.
During the course of Pokémon Ruby and Sapphire, Team Magma or Team Aqua, depending on version, seek out Groudon or Kyogre, respectively, with the intention of awakening them to make more homes for Pokémon of the land or sea. Eventually, the plan goes awry, and the player is forced to defeat or capture the legendary to stop a global disaster. In Pokémon Emerald, instead, both teams are on the loose, intending to awaken their respective legendary target, and only with interference by the player and Rayquaza does the fight end up resolved.

Jirachi is known to grant wishes written on the tags on its head each time it awakens: once every millennium.
In the games, Jirachi has never had a concrete location tied to it, and it cannot be captured from the wild legitimately. However, several direct transfers have been present in the history of the franchise, most notably in the form of a bonus disc released as a preview of Pokémon Colosseum which fixes the Berry glitch present in Pokémon Ruby and Sapphire.
Jirachi starred in Jirachi: Wish Maker, where it befriended Max as the group attempted to keep it away from Butler, a former Team Magma operative.

Deoxys A virus from space which mutated when shot by a laser, was the first legendary Pokémon known to change form, taking different forms. They got 4 formes which is Normal Forme in Pokémon Ruby and Sapphire, Attack Forme in Pokémon FireRed, Defense Forme in Pokémon LeafGreen, and Speed Forme in Pokémon Emerald.

Lake guardians, the name for those pokemon. The Sinnoh's native legendary trio, represent the spirit of all consciousness, with Uxie embodying knowledge, Mesprit embodying emotion, and Azelf embodying willpower. According to legend, having been created by the Original One, the trio have the power to tame the powerful dragons it also created.
In the games, Uxie, Mesprit, and Azelf are found in the caverns of Lake Acuity, Lake Verity, and Lake Valor, respectively, though Mesprit will roam Sinnoh after the player has encountered it, rather than battle immediately as the other two will. The trio are captured by Team Galactic's Commanders, Jupiter, Mars, and Saturn, and subjected to the experiments of Charon to draw out the Red Chain from the gems in their bodies. Cyrus summons the legendary dragons of Sinnoh mythology, and alone, the lake guardians' power is not enough to stop Dialga and Palkia. Giratina interferes and draws Cyrus into the Distortion World, where the lake guardians assist the player in navigation toward Giratina's lair.

The legendary creators of the Pokémon universe, the Dragon trio consisting of Dialga of time, Palkia of space, and Giratina of antimatter, are, like the weather trio before them, the mascots of Sinnoh's trio of games, Pokémon Diamond, Pearl, and Platinum.
In the games, Dialga and Palkia are sought by Cyrus to destroy and then remake the universe without spirit, a thing he hates about humanity. At Spear Pillar, one of the two will be able to be captured in Diamond and Pearl, depending on the game, while Giratina may be obtained after the Pokémon League has been conquered. In Platinum, however, Giratina interferes with Cyrus's planned destruction of the universe, and may be captured in its home, the Distortion World, while Dialga and Palkia cannot be found until the Elite Four have been defeated.

Cresselia and Darkrai represent two phases of the moon with opposite connotations: Darkrai represents the new moon, the cause of the darkest nights and bringer of nightmares, while Cresselia represents the crescent moon, a sign of hope and good dreams. 

 

The sea guardian Pokémon are a legendary duo that, like Mewtwo and Mew, is comprised of a parent and child. Manaphy, a legendary Pokémon that makes its home in warmer seas south of the known regions, bears Phione when bred in captivity in the known regions. Manaphy can only be found through an event: either it may be transferred in its egg from one of the Ranger games after activating an event in those games, or can be directly received via various Mystery Gift events. Like Jirachi, it cannot be legitimately found in the wild. Phione, of course, must be bred from a Manaphy and a Ditto, making it the only legendary Pokémon available only through this method.

Heatran is the embodiment of all volcanic activity, appearing in Stark Mountain in Sinnoh, where it was said to have been born at the same time as Dialga, Palkia, and Giratina created Sinnoh at Spear Pillar and created the Battle Zone. Heatran is the first, and currently only, legendary Pokémon with a variable gender.
Heatran first appeared in the anime in Arceus and the Jewel of Life, under the control of Marcus, and later appeared in DP169 as part of a Pokémon Ranger rescue mission.

Regigigas is the master of the legendary golems, having created them in ancient times.This pokemon can be say as a combination of regice, registeel and regirock.
In the games, Regigigas is found at Snowpoint Temple, though it will not awaken unless all three of the legendary golems are in the player's party.
Regigigas appeared in the anime in Giratina and the Sky Warrior, where it attempted to stop a glacier from destroying Gracidea. Another appeared in Pillars of Friendship!, where it was hunted by J and defended by Brandon.

Shaymin, A legendary Pokémon that has the ability to purify areas instantly and bring plant life in abundance, Shaymin is referred to as the Mew of Generation IV. Unlike previous event legendaries with its straight-100 base stats, however, Shaymin has the ability to change forms, between Land Forme and Sky Forme. 

Arceus is, according to legend, the creator of the Pokémon universe. Born of an egg in the chaos at the beginning, Arceus's powers were awakened immediately, and from itself it made time and space, matter and antimatter, and set Dialga, Palkia, and Giratina to guard them. It created spirit as well, setting Uxie in charge of knowledge, Mesprit in charge of emotion, and Azelf in charge of willpower, before falling into an eternal slumber.

Arceus can be awoken from its sleep using an Azure Flute at Spear Pillar, which will open a staircase to its home, the Hall of Origin. There it can be captured, though no legitimate way of obtaining the Azure Flute has yet been released.