Legendary Pokemon are coming Pokemon Go in celebration of the game's one-year anniversary.

Set to coincide with the Pokemon Go Fest event in Grant Park, Chicago, the first legendary Pokemon will become available for capture this weekend.

As Trainers around the world go out and explore their neighbourhoods in search of Pokemon and raid battles, they can keep an eye out for unique legendary eggs appearing at Gyms. If trainers and their team are able to successfully defeat a legendary raid boss, they will have the opportunity to catch a legendary pokemon of their own.

A new trailer has depicted a horde of trainers taking on Articuni, Zapdos, Moltres, Lugia, and Ho-oh, which may indicate that the birds could be among the first legendaries to be released into the game. The trailer also featured a brief appearance from Mewtwo.

Pokemon Go's anniversary event is already underway, with a Pikachu wearing Ash's iconic hat available for capture. Loot boxes are also available for purchase that include Raid passes, however it is unclear whether these will be necessary to partake in a legendary raid battle.