The Royal Enfield model used in the movie "Arjun Reddy" is the Royal Enfield Bullet 500. This model is known for its classic design and powerful performance. In the movie, the protagonist Arjun Reddy, played by Vijay Deverakonda, is often seen riding this iconic motorcycle. The Bullet 500 is a popular choice among Royal Enfield enthusiasts and has a strong presence in the Indian biking community.