
The deal comes as O2's period of exclusivity with Apple draws to an end. O2 has held an exclusive iPhone deal with Apple since 2007, but will continue to offer the phone to its customers.
Orange UK customers will be able to use the iPhone later this year. Apple already offers iPhones in 28 countries and territories.
Orange will sell iPhone in Orange shops, on the Orange webshop, via Orange telesales and in selected high street retailers.
An O2 spokesman said: "We're proud that we have been able to offer an exclusive iPhone deal to our 20 million customers for the past two years.
"We always knew iPhone exclusivity was for a limited period of time, but our relationship with Apple continues and will be an ongoing success. We have more than one million iPhone customers and they remain very important to us."
Earlier this month, Orange said it planned to merge its UK operations with T-Mobile to leapfrog O2 and create the country's largest mobile phone provider, with 28.4 million customers.