It comes days after Downing Street refused to comment on reports the pair were planning a “lavish” summer wedding.
Boris Johnson has married fiancée Carrie Symonds in a surprise ceremony, Sky News understands.
The prime minister, 56, tied the knot with Ms Symonds, 33, in a small ceremony at Westminster Cathedral on Saturday.
It comes just a few days after Downing Street refused to comment on reports the pair were planning a “lavish” summer wedding.
It was reported the couple had sent out “save the date” cards telling family and friends to keep 30 July 2022 free for celebrations.
The couple were the first unmarried pair to live in Downing Street
The couple became engaged on the island of Mustique in late 2019 and have a one-year-old son, Wilfred.
The marriage is Mr Johnson’s third.
The Sun reported that the ceremony at the Catholic cathedral was carried out by Father Daniel Humphreys who had given the couple pre-marriage instructions, and baptised Wilfred last year.
Shortly after 1.30pm, the Byzantine-style church was suddenly cleared of visitors, with staff saying it was going into lockdown, the newspaper said.
Half an hour later, a limousine carrying the bride swept into the piazza outside the main west door.
Ms Symonds wore a long white dress but not a veil, according to The Sun.
He was previously married at the age of 23 to Allegra Motyn-Owen in 1987.
He later married Marina Wheeler in 1993, but they separated in 2018. They have two daughters, Lara Lettice, 26, and Cassia Peaches, 22, and two sons Milo Arthur, 24, and Theodore Apollo, 20.
The PM also has another child, Stephanie Macintyre, with art consultant Helen Macintyre.
Weddings in England are currently subject to strict coronavirus restrictions and only up to 30 people in COVID-secure venues are allowed.
But dancing is advised against due to the increased risk of transmission, except for the couple’s traditional first dance.
The wedding comes at the end of a difficult week for the prime minister in which his former aide Dominic Cummings branded him unfit for office.
The prime minister’s former aide said Ms Symonds had been desperate to oust him from his role as Mr Johnson’s right-hand man, and had sought to put her own friends in key positions.
Mr Cummings also claimed that in February 2020, when the pandemic was becoming a major global crisis, Mr Johnson was “distracted by finalising his divorce, his girlfriend wanted to announce being pregnant and an engagement, and his finances”.
Work and Pensions Secretary Therese Coffey tweeted a message of congratulations to the couple.
“Congratulations @BorisJohnson and @carriesymonds on your marriage,” the cabinet minister said.
She was joined by Northern Ireland’s First Minister Arlene Foster, who tweeted: “Huge congratulations to Boris Johnson & Carrie Symonds on your wedding.”
But former Labour frontbencher Jon Trickett said the wedding was “a good way to bury this week’s bad news” on Mr Cummings’ testimony, the spread of the Indian coronavirus variant and the row about funding of the Downing Street flat.