What is the name of the Defense Against the Dark Arts teacher in Harry's second year?

The Defense Against the Dark Arts teacher in Harry's second year was Gilderoy Lockhart. He joined Hogwarts in Harry Potter and the Chamber of Secrets, arriving as a celebrated author whose books described supposedly heroic encounters with dark creatures.

Lockhart’s fame was built on stolen achievements. He located witches and wizards who had genuinely defeated dangerous beings, learned their stories, and then erased their memories before publishing the victories under his own name. His polished smile, elaborate robes, and constant autograph-signing made him popular with many students, although other teachers quickly recognized his vanity and incompetence.

His fraud is exposed when Harry, Ron, and Lockhart enter the Chamber of Secrets. Lockhart tries to use a Memory Charm on the boys, but Ron’s damaged wand causes the spell to rebound. Lockhart loses his own memory and is later seen receiving care at St Mungo’s Hospital for Magical Maladies and Injuries.

The common mix-up is with Quirinus Quirrell, who taught Defence Against the Dark Arts during Harry’s first year, and Remus Lupin, who taught it during Harry’s third year. Lockhart’s Hogwarts tenure lasted only Harry’s second year.