The Prime Minister has praised the capital in her message for Pride 2017, saying London sends a "proud and positive message to the world".
Theresa May is currently in Hamburg for the G20 summit, where she has also been holding bilateral talks with US President Donald Trump, but released a message to coincide with the occasion.
Pride brings people together in joyful celebration of our values of freedom, tolerance and equality. It is a vivid display of the diversity which makes London one of the greatest cities in the world.
And at its heart, it is about a simple thing: love. That’s why this year’s theme – ‘Love happens here’ couldn’t be more appropriate. It captures perfectly the warmth of this wonderful city and its people.
This year also marks 50 years since parliament repealed the laws which criminalised homosexuality in England and Wales. May said the anniversary reflects how far society has come, but also "reminds us how much still remains to be done".
She also reiterated the UK's pledge to encourage other countries to ensure equal rights for all.
"Around the world, cruel and discriminatory laws still exist – some of them directly based on the very laws which were repealed in this country fifty years ago," May said. "So the UK has a responsibility to stand up for our values and to promote the rights of LGBT+ people internationally."
Labour leader Jeremy Corbyn also released a message, saying Pride "gives us an opportunity to reflect on key achievements in the long and ongoing struggle for LGBT+ rights".
Thousands are expected to take part in the capital's annual Pride parade today, which starts at Portland Place and finishes at Whitehall.