Customers rushed to buy the new handsets
Staff cheered as throngs of excited customers made their way into Apple's flagship store in London.
A small number of Apple fans keen to get hold of the handset had started queuing at stores overnight and numbers swelled to around 300 for the launch.
First out of the store with the £269 internet enabled device was 20-year-old north London student Tom Jasinski who said "It was worth the wait".
"I got here 26 hours ago," he told PA. "It is a great piece of hardware. It is a great thing and I love it."
The BBC's Rory Cellan-Jones described the scene in London as "mayhem".
He said before the doors opened at the store, Apple staff were walking up and down the lines of people "whipping them into a frenzy".
The internet enabled handset has also gone on sale at more than 1,300 other stores around the UK with each customer limited to two handsets each.
The first European handsets were sold at the T-Mobile store in Cologne, Germany just after midnight on Friday morning.
T-Mobile's parent company Deutsche Telekom said it had sold over 10,000 iPhones in Germany by late afternoon.
"It was love at first sight," one 50-year-old man told Reuters news agency.
The iPhone will go on sale in France on 29 November and Asia in 2008.
Although the wait is over for some fans, there are concerns that consumers are only able to use the phone with the 02 mobile network.
The phones can be unlocked for use on other networks but this voids the warranty and could break the device if software updates from Apple are installed.
As many as 250,000 users in the US have unlocked the device using free and paid-for software to make the phone work on different networks, and to load third-party software not supported by Apple.
Critics have pointed out that the device, while boasting an innovative user interface which makes it simple to use, lacks technology found in rival phones.
The iPhone only works on slower 2G networks, limiting its usefulness as a mobile web browser, but it does also connect to wi-fi hotspots.
In the UK, iPhone owners can connect to the net for free at thousands of The Cloud's hotspots.
Greg Joswiak, head of marketing for the iPhone, denied that the phone had sacrificed function over form by choosing 2G.
"We wanted to make sure that we had a very small device and good battery life. You can't do that today with 3G.
"It's just too power hungry, which is why most 3G phones have nowhere near eight hours of talktime."
One of the iPhone's big rivals, the Nokia N95, has four hours of talk time on a 2G network, while Apple's device has up to eight hours, according to technical specifications provided by both firms.
Customers have to pay in advance for the iPhone and cannot get it free on a mobile contract.
The Apple phones costs £269 and the minimum monthly contract with O2 is £35.
Jonathan Arber, an analyst with Ovum, said: "In the long term it will be interesting to see how consumers will react to having to pay for this device.
"Obviously in the UK most consumers are used to getting their devices for free."
Mr Arber also pointed out that the UK mobile market is predominantly made up of pre-pay users.
"That's a huge section of the market that is not going to be purchasing an iPhone. In the contract segment there are a lot of people who are not going to pay £35 a month.
"But for a large group of people the iPhone is certainly an attractive proposition."
According to analysts M:Metrics 10% of 16,000 mobile phone users surveyed in the UK expressed strong interest in buying the iPhone.
Fifty per cent of the survey sample with a strong interest had not paid for their current phone and almost half were on a pre-pay contract.
Apple has sold 1.4 million iPhones since it went on sale in the US and O2 and T-Mobile are expecting strong sales.
"We assume that the device will find a very good reception on the market," said Rene Bresgen, a spokesman for Deutsche Telekom, owners of T-Mobile in Germany.
More than a 1,000 O2 shops, Carphone Warehouse stores and Apple shops are expected to sell the device.
Some iPhone owners in the UK have not been content to wait for the official release and have bought the device in the US and unlocked it for use on any network.
One owner, called Daryl, told BBC News he had bought 14 phones in the US for himself and friends and unlocked them.
He said he had unlocked his original phone because he didn't want to be tied to one network.
"I like the current network I am on and I'd like to stay with that network. I don't like be imposed upon as to which network I want to switch to.