Albus Dumbledore dies in the sixth book of the Harry Potter series, titled Harry Potter and the Half-Blood Prince.
In this book, Dumbledore is killed by Severus Snape during the Battle of the Astronomy Tower. This event is a pivotal moment in the series, as it marks a significant turning point in the fight against Voldemort. Dumbledore’s death leaves Harry and his friends to continue the battle without his guidance and protection.