In front of a congregation of about 100 world leaders and a television audience of millions, the Archbishop of Canterbury, the spiritual leader of the Anglican Church, slowly placed the 360-year-old St Edward's Crown on Charles' head as he sat upon a 14th-century throne in Westminster Abbey.
Charles' second wife Camilla, 75, was also crowned Queen during the two-hour ceremony, which while rooted in history, is also an attempt to present a forward-looking monarchy, with those involved in the service reflecting a more diverse Britain and leaders from all faiths.
For a nation struggling to find its way in the political maelstrom after its exit from the European Union and maintain its standing in a new world order, its supporters say the royal family provides an international draw, a vital diplomatic tool and a means of staying on the world stage.
The event was estimated to cost around $188 million.
Charles automatically succeeded his mother as king on her death last September, and the coronation is not essential but regarded as a means to legitimise the monarch in a public way.