Monster Rancher 4 is a monster-raising simulation game by Tecmo, officially released on August 14, 2003. The game was developed as a continuation of the popular Monster Rancher series, building on the mechanics and features of its predecessors while introducing new elements to enhance gameplay.

In Monster Rancher 4, players can breed and train multiple monsters simultaneously, utilizing a variety of training equipment and customizing their training facilities for optimal results. The game emphasizes strategic planning in training to improve monster performance in battles.

The storyline of Monster Rancher 4 revolves around the player's journey to become a top monster trainer, exploring various environments and engaging in battles while discovering new monsters. Players can unlock these monsters by inserting other CDs and DVDs into their console, adding a unique twist to the gameplay.

Monster Rancher 4 stands out with its innovative use of real-world media to generate in-game content, allowing for a diverse range of monsters and enhancing the overall experience of monster collection and training.