From Bulbapedia, the community-driven Pokémon encyclopedia.
Bewilder Forest (Japanese: 迷いの森 Bewilder Forest) is an anime-exclusive location in the Sinnoh region. It is located between Sandgem Town and Jubilife City and is famous for the Stantler that live there.
This location was featured in Different Strokes for Different Blokes. Ash's rival Paul caught two Pokémon here: an Ursaring and a Stantler. Stantler was released in the same episode, but Ursaring remains on his team.
Ash fought Paul in a battle here. Ash's somewhat mistrusting Turtwig began to obey his commands in this battle, but ultimately Turtwig was defeated by Paul's Chimchar.