During an elaborate ceremony at St James’ Palace in London on Saturday, Charles III swore an oath and was proclaimed king.
The Accession Council formally announced the death of his mother, Queen Elizabeth II.
Charles III was crowned king shortly after that.
Before the documents were signed, about 200 people gathered in the room all said, “God save the King.”
Flags that were lowered in mourning for the late Queen will be flown at half-mast for a short time, according to the BBC.
In his first address to the nation yesterday, the King pledged to emulate his “darling mama’s” life of service.
The Queen, the United Kingdom’s longest-reigning monarch, died peacefully on Thursday afternoon at the age of 96 at Balmoral Castle.