Is Hostel based on a true story?

No, the Hostel movies are not based on a true story. They are labeled "based on a true story," but this is essentially a lie.

Writer/director Eli Roth got the idea for the Hostel movies from a website that a friend showed him. The website advertised a "murder vacation" in Thailand, where for $10,000, you could shoot someone in the head.

He has no idea if the website was real, or just a hoax.