The handset took just three days to reach the milestone through combined sales in the US, Australia, Canada, France, Germany, Hong Kong, Japan, Singapore and the UK.
Apple also confirmed that its iOS 6 operating system has been downloaded on more than 100m devices since it went live on September 19.
"Demand for iPhone 5 has been incredible and we are working hard to get an iPhone 5 into the hands of every customer who wants one as quickly as possible," said Apple CEO Tim Cook.
"While we have sold out of our initial supply, stores continue to receive iPhone 5 shipments regularly and customers can continue to order online and receive an estimated delivery date. We appreciate everyone's patience and are working hard to build enough iPhone 5s for everyone."
The iPhone 5 will be released in 22 more countries on September 28, and be available in more than 100 countries by the end of the year.
Watch Digital Spy's video review of iOS 6 below:
iPhone 5 goes on sale
Copyright: PA Images Bebeto Matthews/AP