Azkaban is the fictional prison that appears in J.K. Rowling’s Harry Potter series.
Azkaban is located on an island and is guarded by Dementors for much of the series. It serves as the wizarding world’s high-security prison, holding people convicted of serious crimes. The prison is first discussed prominently in Harry Potter and the Prisoner of Azkaban.
Sirius Black’s escape is one of the central events linked to Azkaban. He is wrongly imprisoned for years before the truth about Peter Pettigrew emerges. Other important prisoners include Bellatrix Lestrange and several Death Eaters.
Azkaban is often confused with Nurmengard, another wizarding prison associated with Gellert Grindelwald. Hogsmeade is a village, while Gringotts is the wizarding bank in Diagon Alley. These places all belong to Rowling’s fictional world, but only Azkaban is the prison named in this question.