Harry Potter is the lead character in a phenomenally successful series of children's books written by the Scottish author JK Rowling. It was subsequently made into a series of movies.
Famously Rowling (whose first name is Joanne, but publishers were concerned a female name would put off boy readers) was rejected by 12 publishers before Bloomsbury published Harry Potter and the Philosopher's Stone. It was with the fourth book in the series, Harry Potter and the Goblet of Fire, that Rowling really got major attention, and Harry became a cult figure.
Harry ages with each book, being very much a child in the beginning, but by the Half-Blood Prince he's an adolescent, and almost an adult by the conclusion of the final book, Harry Potter and the Deathly Hallows, he's virtually an adult.