Can legendary Pokemon evolve or undergo Mega Evolution?


I have not seen any evolution of Legendary Pokémon yet. I'm not talking about
[pseudo-legendary Pokémon](https://bulbapedia.bulbagarden.net/wiki/Pseudo-
legendary_Pok%C3%A9mon).

I did some more research and found that [Mewtwo can Mega
Evolve](https://bulbapedia.bulbagarden.net/wiki/Mewtwo_\(Pok%C3%A9mon\)), but
it is not a natural Legendary Pokémon, it is a man-made clone of Mew.




As of Gen VIII, there are only two Legendary Pokémon capable of evolving:

  * Cosmog, which evolves into Cosmoem, and then into either Solgaleo or Lunala
  * Meltan, which evolves into Melmetal

Both are shown doing this in the _Sun and Moon_ anime: Cosmog while under
Lillie's ownership, and Meltan while under Ash's ownership.

The following Legendary Pokémon (discounting Mewtwo) are capable of undergoing
Mega Evolution and have been shown doing so in the anime:

  * Latias and Latios (seen in the anime movie _[Hoopa and the Clash of Ages](https://bulbapedia.bulbagarden.net/wiki/M18)_ )
  * Rayquaza (seen in the [Mega Evolution Specials](https://bulbapedia.bulbagarden.net/wiki/XYS02) and in _Hoopa and the Clash of Ages_ )
  * Diancie (seen in the anime movie _[Diancie and the Cocoon of Destruction](https://bulbapedia.bulbagarden.net/wiki/M17)_ )

Groudon and Kyogre are also capable of undergoing a process called Primal
Reversion that is very similar to Mega Evolution but not quite the same. They
are shown doing this in the Mega Evolution Specials, _Hoopa and the Clash of
Ages_ , and in _Pokémon Generations_.




As of Gen VIII, there are only two Legendary Pokémon capable of evolving:

  * Cosmog, which evolves into Cosmoem, and then into either Solgaleo or Lunala
  * Meltan, which evolves into Melmetal

Both are shown doing this in the _Sun and Moon_ anime: Cosmog while under
Lillie's ownership, and Meltan while under Ash's ownership.

The following Legendary Pokémon (discounting Mewtwo) are capable of undergoing
Mega Evolution and have been shown doing so in the anime:

  * Latias and Latios (seen in the anime movie _[Hoopa and the Clash of Ages](https://bulbapedia.bulbagarden.net/wiki/M18)_ )
  * Rayquaza (seen in the [Mega Evolution Specials](https://bulbapedia.bulbagarden.net/wiki/XYS02) and in _Hoopa and the Clash of Ages_ )
  * Diancie (seen in the anime movie _[Diancie and the Cocoon of Destruction](https://bulbapedia.bulbagarden.net/wiki/M17)_ )

Groudon and Kyogre are also capable of undergoing a process called Primal
Reversion that is very similar to Mega Evolution but not quite the same. They
are shown doing this in the Mega Evolution Specials, _Hoopa and the Clash of
Ages_ , and in _Pokémon Generations_.

