The company's parent company Telefonica will also sell the phone exclusively in Spain, Ireland and Germany.
No official launch date for the iPhone-killing smartphone has been announced, but O2 says the portable internet device will be in shops before Christmas.
Customers who want to be notified when the Palm Pre is going to be available can register at www.palm.com/uk-pre-notify.
The Palm Pre is Palm's big effort to get back into the upper echelons of the mobile device market. The first smartphone to be on Palm's much-anticipated WebOS operating system, the Palm Pre pulls information from your phone, desktop and the web into a single, integrated view.
The phone has proved to be an early breakthrough success in the US, where Palm has been struggling to compete with mobile internet-enabled smartphones such as Apple's iPhone and Google Android handsets such as the HTC-built T-Mobile G1.
With a large touchscreen that many reviewers consider superior to Apple's iPhone, as well as a slide-out qwerty keyboard, the Palm Pre is considered by many to be the first genuine competitor for Apple's über-popular smartphone: also available exclusively via O2. Unfortunately, some US customers have complained about 'shoddy' build quality on the Palm Pre.
"We are fast becoming the home of the smartphone with the addition of the hotly-anticipated Palm Pre to our already extensive portfolio," said Matthew Key, chairman and chief executive officer, Telefónica Europe.
"Our customers will be the first outside of North America to experience one of the most successful mobile devices of the year.
"Europe continues to be an important region for Palm, and we're proud to work with O2 and Movistar to spread the excitement Palm Pre has already ignited in North America," said Jon Rubinstein, Palm chairman and chief executive officer.
"Since we showed Palm Pre at Mobile World Congress in February, there's been a great deal of anticipation for an announcement about European availability, and that day is here."