The Diamond Diadem, historically known as the George IV State Diadem, is a diadem that was made in 1820 for King George IV. The diadem has been worn by queens regnant and queens consort in procession to coronations and State Openings of Parliament. It has been featured in paintings and on stamps and currency.
The diadem was most recently worn by Queen Camilla of the United Kingdom at the 2024 State Opening of Parliament.