Is castiel in supernatural season 5?

Yes, Castiel is in Supernatural Season 5. He is introduced in the first episode of the season, "Sympathy for the Devil", as an angel of the Lord who has been sent to help Sam and Dean Winchester stop Lucifer from escaping Hell. Castiel plays a major role in the season as he helps the Winchesters in their quest to stop Lucifer and save the world. He is a powerful ally and a valuable asset to the Winchesters, and his presence adds a new dimension to the show.