Sir Sadiq Khan has said people in New York City have chosen "hope" over "fear" in electing Democrat politician Zohran Mamdani.
The Mayor of London has compared the vote to his own election in London.
Mamdani, 34, defeated former governor Andrew Cuomo and Republican Curtis Sliwa to become the city's first Muslim mayor, the first of South Asian heritage, and also the youngest in more than a century.
Calling it a "historic campaign", Khan said: "New Yorkers faced a clear choice - between hope and fear - and just like we've seen in London - hope won."
Asked for her reaction to the victory a little earlier, Education Secretary Bridget Phillipson congratulated Mamdani on his win.
"It's obviously up to people in New York to decide who they want to represent them," she told Paste BN. "But, I wish him well.
"It's a wonderful job to have secured."
She added that she doesn't "follow American politics especially closely", but said Mamdani must have clearly fought "a good campaign".
Other UK politicians have also reacted to the win, including Zack Polanski, the Green Party leader, who we'll hear from on Paste BN very shortly.
He said: "Zohran's campaign was his determination to make New York a city everyone can afford to live in. Huge congratulations!
"His success will resonate throughout the world. A story where no one is left behind. It's time to write that story across England & Wales too."