Warner streams films over Facebook, opening up a new revenue stream for the social network.
According to Warner, consumers will pay for a select few movies using Facebook Credits, the virtual currency that has so far mainly been used in social games on the site.
Facebook, which makes money mostly through online advertising, takes 30% of the revenue of sales by third parties on the website using Credits.
The service will initially be available in the US, the company said, but could be made more widely available at a later date, with more titles added to the catalogue.
The streaming of full-length Hollywood films on Facebook creates a new role for the 500m member network, and could provide a threat to film specialists such as LoveFilm and Netflix.
"The 'wisdom of friends' could be a bigger driver of movie viewership than the 'wisdom of crowds'," said Goldman Sachs analyst Ingrid Chung in a note to investors.
Film rentals cost 30 Facebook Credits, or $3, for 48 hours, and viewers can pause and restart a movie whenever they log back in.
