To put that in perspective, it took Twitter four times longer to secure a global audience of 1m, while Facebook and Foursquare secured an equal amount in about 14 months.
The company credits the growth to its comedy and drama content, which it claims are the most popular among UK and Irish viewers.
Netflix CEO Reed Hastings said: “This membership milestone is evidence that Netflix has rapidly gained popularity in the UK and Ireland.”
“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.”
The news follows a YouGov survey that suggested 10 per cent of consumers are now devoting 2 hours or more of their day to watch TV shows online.