Much like the other two Pokemon apart of the Legendary Bird Trio, Articuno can be found at any point during the Main Storyline (or Post Game should you so wish to wait until then). Articuno can be found deep within the Seafoam Islands, which are located just off of Cinnabar Island. Like other Legendary Pokemon Encounters found within the game, Articuno must first be defeated in battle before you will be allowed to capture it. In battle, Articuno will be at Level 50 and will have all of its Stats boosted at the beginning of said bout, knowing the moves of Mirror Coat, Agility, Ice Beam and Reflect. After capturing Articuno in the Seafoam Islands, there is a chance that it will appear as a Special Spawn on certain routes found across the Kanto Region.
Need help Catching Articuno? Check out our How To Easily Catch Articuno Page!