Dumbledore's Army is a student organization formed at Hogwarts School of Witchcraft and Wizardry in the book series by J.K. Rowling. It was created by Harry Potter and his friends to learn practical defense against dark magic, as they felt the official classes were inadequate. The group meets secretly to practice spells and prepare for the challenges they face. The name "Dumbledore's Army" honors Albus Dumbledore, the headmaster of Hogwarts, who supports the fight against dark forces. The group includes members from different houses, primarily Gryffindor, Hufflepuff, and Ravenclaw, and plays a crucial role in resisting the oppressive regime of Dolores Umbridge during their time at Hogwarts.