The deal ends an exclusive arrangement between UK network operator O2 and the Californian phone maker, which has been in place since 2007.
Orange said its customers would be able to buy the phone “later this year” but did not specify a date or pricing.
However, analysts said that in markets where there was already competition there was little difference in handset prices but small variations in tariffs.
“There’s not a lot they can do – they are subsidising the hardware, so they can’t afford to do much on the tariff,” said Carolina Milanesi of Gartner.
“You may see a £30 per month tariff versus £35, but I would not expect anything more.”
Orange recently revealed plans to merge its UK network with Deutsche Telekom’s T-Mobile to create a business with 28.4 million customers.
If given the go-ahead, it would be the UK’s largest provider, overtaking Telefonica’s O2, with about 37% of the mobile market.
“That would be good for Apple,” Dave McQueen, principal analyst at Informa Telecoms and Media told BBC News.
“Then, around three quarters of the UK market will then have access to the iPhone.”
O2 has offered the handset in the UK since its launch in 2007. In February, it said it had sold more than one million of the handsets.
The launch of the latest iPhone 3GS in June significantly boosted sales, with many stores running out of stock.
The phone has also allowed the firm to win subscribers from other networks, according to analysts.
However, the rise of smartphones – which have the ability to surf the web and send e-mail – has put a burden on the O2 network, according to Mr McQueen.
“IPhone users to tend to use data quite extensively – perhaps more than anticipated,” he said.
“Orange has always a good data network and if the T-mobile deal goes through it would allow them to share the burden.”
O2 will continue to sell the handset in Britain, alongside iPhone rival the Palm Pre.
The Palm phone, described by some as an “iPhone killer”, will be available exclusively to O2 from 16 October.
O2 said that it always knew that its exclusive deal was for “a limited period of time”.
The new agreement with Orange brings the UK into line with many other countries around the world which have multiple operators that offer the iPhone.
In countries where exclusive deals still persist, such as the US, some customers choose to “unlock” their phones using third party software so they work on an unlicensed network.
However, Apple has warned that the practice can cause “irreparable” damage to a handset and has engaged in a game of cat-and-mouse, releasing periodic software updates which prevent unlocked phones from working correctly.
Originally posted at BBC.co.uk