Lèse-majesté () or lese-majesty () is an offence against the dignity of a ruling head of state (traditionally a monarch but now more often a president) or the state itself. The English name for this crime is a borrowing from the French, where it means "a crime against The Crown."

This behaviour was first classified as a criminal offence against the dignity of the Roman Republic of ancient Rome. In the Dominate, or Late Empire period, the emperors eliminated the republican trappings of their predecessors and began to equate the state with themselves. Although legally the princeps civitatis (his official title, meaning, roughly, 'first citizen') could never become a sovereign because the republic was never officially abolished, emperors were deified as divus, first posthumously but by the Dominate period while reigning. Deified emperors enjoyed the same legal protection that was accorded to the divinities of the state cult; by the time it was replaced by Christianity, what was in all but name a monarchical tradition had already become well-established.

Narrower conceptions of offences against Majesty as offences against the crown predominated in the European kingdoms that emerged in the early medieval period. In feudal Europe, some crimes were classified as lèse-majesté even if they were not intentionally directed against the crown. An example is counterfeiting, so classified because coins bore the monarch's effigy and/or coat of arms.

With the disappearance of absolute monarchy in Europe, lèse-majesté came to be viewed as a less-serious crime. However, certain malicious acts that would have once been classified as the crime of lèse-majesté could still be prosecuted as treason. Future republics that emerged as great powers generally still classified as a crime any offence against the highest representatives of the state. These laws are still applied as well in monarchies outside of Europe, notably in modern Thailand and Cambodia.