The phrase was spoken in seven languages around two minutes past midnight as the city skyline filled with lights in the largest annual display in Europe.
A soundtrack featuring Europe’s finest musical artists celebrated the diversity of the capital, after Big Ben, silent for much of 2018 due to renovations, chimed once more.
Mayor of London Sadiq Khan said the sold-out display showed Europe that the capital will remain "open-minded" and "outward looking" post-Brexit.
He said Westminster politicians had given the world the impression that Britain is "insular, inward looking", as Britain begins the new year countdown to Brexit.
Mr Khan said he hoped this year’s event would "send a message of support" to the more than one million European citizens for whom London is home.
He has previously expressed his backing for a People's Vote and has voiced his concerns over the effects of a no-deal Brexit on the capital.
"One of the things which upset many, many Londoners and many people across our country and in Europe is the tone and language used by politicians in Westminster, giving the impression we’re insular, inward looking, not welcoming to Europeans," Mr Khan said.
He vowed that London would remain the same after March 29, and said the fireworks display was about "showing the world, while they’re watching us, that we’re going to carry on being open-minded, outward looking, pluralistic".
Mr Khan continued: "We, in my opinion, are one of the greatest cities in the world, one of the reason we are one of the greatest cities in the world is because of the contribution made by Europeans.
"I think diversity is a strength and I think what tonight is about is celebrating that diversity.
"I hope that members of Parliament, members of the Government will see the fireworks tonight, will listen to the soundtrack and will reflect on what sort of country they want to live in post-March."