Nicola Mendelsohn, vice president for Facebook Europe, Middle East and Asia, said: "The UK's flourishing entrepreneurial ecosystem and global reputation for engineering excellence makes it one of the best places in the world to build a tech company".
Located in Rathbone Place, Facebook's new office will be home to 800 new "high tech" employees.
The social media giant will employ some 2,300 people in the U.K.by the end of 2018 - a vote of confidence in London despite Britain's looming departure from the European Union.
The office would result in the creation of close to 800 new jobs for the country by 2018.
Nicola Mendelsohn, Facebook's vice president for Europe, the Middle East and Asia, said: "The UK's flourishing entrepreneurial ecosystem and worldwide reputation for engineering excellence makes it one of the best places in the world to build a tech company".
"We have chosen the United Kingdom for this project because this country is, and always has been, a powerhouse of innovation", said Facebook in a website post.
Facebook experts from a range of disciplines including engineering, product and partnerships, will share their knowledge, expertise and mentorship as part of the programme.
"And we've built our company here - this country has been a huge part of Facebook's story over the past decade, and I look forward to continuing our work".
The 247,000-square-foot (75,285-square-meter) office, designed by architect Frank Gehry, opened Monday.
As well as engineers, there will also be developers, marketing and sales teams.
The new office is situated away from the Oxford Street which is the Europe's favorite shopping area and integrates first in-house association incubator called LDN_LAB.