Scores of people gathered in Woolwich, Eltham and Greenwich to mark the royal accolade, awarded as a special tribute for the Queen's Diamond Jubilee year.
The accolade reflects the borough's historic links with the monarchy - from Eltham Palace to the Old Royal Naval College.
It became the first new royal borough in more than 85 years, following the likes of Kensington and Chelsea, Windsor and Maidenhead and, most recently, Kingston.
The borough will receive no financial gain from the status directly. However, the council believes the borough's new-found status will attract further investment in the area, and embolden locals with a sense of pride in their area.
Councillor Chris Roberts, Leader of Greenwich Council, said: 'This is a proud day for Greenwich and its people, and reflects centuries of close associations between the Borough and the monarchy.
'Our new Royal Borough status will drive forward our record levels of regeneration and cement our role as a key international destination for businesses and visitors from across the globe.'
Locals also appeared excited by the accolade. Erike Obulo, 33, of Friendly Street, Deptford, said: 'I was born here and I think it is great. It has a great ring to it. It's fantastic the Queen thinks so highly of Greenwich.'
Greenwich Market trader Kweku Quagrine, 28, said: 'I think it is long overdue. It is an historical borough and deserves royal status.
'It is about time Greenwich was recognised for what it is. There is the Cutty Sark and the Meridian Line. It can only be a positive thing for the area.'
A new crest has been designed, and the council's royal logo is already adorning some new street signs - others will be upgraded as and when it is required.
More than 18 million tourists visit Greenwich each year, worth a hefty £774 million to the local economy. Tourists renting London apartments can explore the royal borough and all it has to offer - from Greenwich market selling crafts and vintage clothing, to The Royal Artillery Museum boasting an array of tanks and cannons.
The accolade was marked with a breath-taking firework display above the snow-covered streets of Greenwich.
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