The smartphone, which is priced at £480 for the 16GB version or £570 for the 32GB capacity, is available from Vodafone's website or high street stores.
The mobile network is also offering customers that buy the handset on pay-as-you-go a free data allowance capped at 250MB per month for a year, along with a year's worth of BT Openzone Wi-Fi access capped at 1GB per month. This offer will be available until November.
"Customers asked us to make the iPhone 4 available on pay as you go, offering them a variety of ways to pay for their mobile internet access," says Mark Bond, Consumer Director, Vodafone UK.
"We'll bring in additional options later in the year which will allow even greater flexibility."
Apple's latest smartphone was unveiled by Steve Jobs at the company's Worldwide Developers Conference (WWDC) in June.
The new handset, which features an all-new design, has "well over 100 new features" including an HD screen, video calling, a gyroscope, a new iMovie app and countless other upgrades.
If you want a pay monthly contract for the iPhone 4, you can compare the best iPhone 4 deals here.