"The Prime Minister warmly congratulates President-elect Macron on his election success.
"France is one of our closest allies and we look forward to working with the new President on a wide range of shared priorities," a Downing Street spokesman said in a statement.
Initial estimates showed Macron, who ran on a centrist platform, won a resounding victory of between 65.5 and 66.1 per cent of the vote.
His far-right rival Marine Le Pen took between 33.9 per cent and 34.5 per cent of votes in the second and decisive round of the presidential election.
Macron in February took his election campaign to London -- home to the majority of an estimated 300,000-plus French citizens in Britain -- where he urged them to bring their talents home to France.