Netflix's UK and Ireland operation, which launched in January, passed 1m members faster than other Netflix business, including the US.
According to Netflix, the growth is four times faster than it took Twitter to hit one million users globally, and nearly twice as fast as it took Facebook and Foursquare - although none of those services were backed by a multi-million advertising budget.
"This membership milestone is evidence that Netflix has rapidly gained popularity in the UK and Ireland," said Netflix chief executive Reed Hastings.
"Our British and Irish members clearly enjoy the ability to instantly watch a large variety of TV shows and films streaming from Netflix on their favourite devices whenever they want."
Netflix now has more than 27 million streaming members worldwide in the United States, Canada, Latin America, the United Kingdom and Ireland.
New competition has also emerged for Netflix in the UK content streaming market in the shape of Sky, which launched its NOW TV internet-TV service this summer.
Aimed at people who have so far abstained from signing up to pay-TV, NOW TV currently offers all content from Sky Movies either via pay-per-view or monthly subscription.
But the scale of demand suggests there is plenty of opportunity for all three players in the market. Netflix has released the results of a survey by YouGov, which indicates that consumers are spending more time enjoying entertainment online.
Around 10% of the UK population now dedicates two hours or more every day to watching TV shows over the internet. Brits spend on average £565.21 a year on new electronic gadgets, with demand for tablets and smartphones particularly high.
Netflix said that comedy and drama are the top genre choices among its UK and Irish members, and the favourite time of the week for streaming entertainment is Sunday night.
Upcoming new content on the service includes movies 50/50, 2012 and Iron Man 2, along with new seasons of Breaking Bad and Damages.