Llywelyn's coronet () is a lost treasure of Welsh history. It is recorded that Llywelyn ap Gruffudd, Prince of Wales and Lord of Aberffraw had deposited this crown () and other items (such as the Cross of Neith) with the monks at Cymer Abbey for safekeeping at the start of his final campaign in 1282. He was killed later that year. It was seized alongside other holy artefacts in 1284 from the ruins of the defeated Kingdom of Gwynedd. Thereafter it was taken to London and presented at the shrine of Edward the Confessor in Westminster Abbey by King Edward I of England as a token of the complete annihilation of the independent Welsh state.