Which came first, Amazon or Harry Potter?

Amazon came first, by 3 years. Jeff Bezos incorporated the company in Washington state.

Side by side

Amazon

Amazon was incorporated on 5 July 1994, originally as Cadabra, and the website opened in July 1995 selling only books. The 1994 incorporation date is used here because it is the company's own founding date; if you mean the shop, 1995 is the answer. Either way it predates Google by three or four years and eBay by about a year.

Harry Potter

Bloomsbury published the first book in June 1997 with a print run of 500 copies, most of which went to libraries, after twelve other publishers had rejected the manuscript. The company's chairman gave the first chapter to his eight-year-old daughter, who demanded the rest. It came out the same year as Netflix was founded and a year before Google.