Huffington Post UK went live this morning with a string of big name contributors including Tony Blair, Alastair Campbell, Ricky Gervais and Sarah Brown.
The UK site is based on the same model as its US counterpart: a mix of original reporting, aggregation, blogging and 'social engagement".
The site is edited by Carla Buzasi, the editor-in-chief of AOL Europe, who has spent the last four months pulling together a 10-strong team of full-time editorial staff and hundreds of part-time contributors from across the UK.
The team includes: political editor Chris Wimpress, a former political correspondent for BBC Radio 4; news editor Jacqui Head, a former online journalist at Al-Jazeera and entertainment editor Caroline Frost, previously an arts producer for BBC News.
Lady Lynn Forester de Rothschild - chief executive officer at EL Rothschild - is the site's editor-at-large.
The team will be supported by the both the wider AOL editorial staff in the UK and the Huffington Post team in the US.
In the build up to the launch several observers questioned whether the website would be able to make an impact on the UK market.
Leading political blogger Guido Fawkes, for example, said that 'far from being daunted Guido welcomes the competition... She [Arianna Huffington] will find us a bit tougher than her past rivals".
Buzasi, the former editor of marieclaire.co.uk, told Press Gazette that 'you kind of expect" such comments when working on a new launch, adding that the website will be looking to work with leading UK bloggers and the mainstream media.
She said the UK site will follow the same model as the US site – 'it's successful for a reason'– but will have a unique voice influenced by traditional 'British wit and humour".
She also claimed that while Huffington Post UK has the 'might of AOL behind us", the relatively small team means it has a 'start-up mentality".
In a statement on the website this morning, founder Arianna Huffington claimed the UK has played a key role in the evolution of the Huffington Post.
'It was July 7, 2005, two months after we'd launched,'she explained. 'I was drinking my morning coffee and reading my paper copy of the New York Times, which had a front-page photo of Londoners celebrating the city's winning bid for the 2012 Olympic Games.
'It was literally yesterday's news. In the meantime, HuffPost not only had the bombings as our news splash but our London-based bloggers weighing in with of-the-moment reactions, bringing home the power and immediacy of real-time, social news.
'And these lessons have gone on to become the defining traits of our approach to delivering news, entertainment, opinion, and information. At the core of everything we do are engagement, connection ('social'), and a commitment to real-time coverage."
She added: 'We are arriving here in the midst of a rich and thriving media culture marked by great innovation. The Guardian's decision to further its commitment to 'open journalism' is particularly exciting, as is the masterful use of storytelling to shine a light on important issues, as demonstrated by The Independent's recent piece on the UK's 'threatened, isolated, under siege' modern working class.
"We look forward to spotlighting and linking to such great stories, driving traffic to them, and fueling conversations around the issues they raise."