In which Harry Potter book does the Battle of Hogwarts take place?

The Battle of Hogwarts takes place in Harry Potter and the Deathly Hallows.

It is the climactic battle of J.K. Rowling’s seven-book series. The conflict begins after Harry, Ron, and Hermione return to Hogwarts while searching for and destroying Voldemort’s remaining Horcruxes. Students, teachers, members of the Order of the Phoenix, and other defenders fight against Voldemort’s forces.

The battle includes several decisive events, including the deaths of Fred Weasley, Remus Lupin, and Nymphadora Tonks. Harry confronts Voldemort in the Great Hall, and the story establishes that Voldemort’s final defeat depends on the Elder Wand’s allegiance as well as Harry’s survival.

The novel was published in 2007. Its title refers to three legendary magical objects—the Elder Wand, Resurrection Stone, and Invisibility Cloak—which become central to the final story.