Grand Stars are special items found in the Super Mario Galaxy video game series. They are awarded to players for completing specific challenges, such as defeating bosses or collecting a certain number of Power Stars. Grand Stars are larger and more significant than regular Power Stars, often unlocking new areas in the game. In the games, collecting a Grand Star typically involves navigating through complex levels and overcoming various obstacles. Once obtained, these stars contribute to the overall progress in the game, allowing players to access new galaxies and continue their adventure in the Mushroom Kingdom.