A federal court in Illinois awarded the damages of $150,000 per movie to Flava Works - the creator of the pornographic films.
The figure is believed to the biggest awarded in a file-sharing case.
The award is thought to be so large because the accused, Kywan Fisher, did not defend himself against claims that he pirated the movies.
In court, Flava Works presented evidence which it said demonstrated that Mr Fisher was the person who put copies of its films on a BitTorrent site.
