Caracalla granted citizenship to nearly all free inhabitants of the Roman Empire in 212 CE.
The measure is known as the Constitutio Antoniniana, or Antonine Constitution. It extended Roman citizenship to almost all free people living within the empire, excluding certain groups such as the dediticii, whose exact legal definition remains debated. The decree was issued during the reign of Emperor Caracalla.
Citizenship brought legal privileges and obligations, including access to Roman civil law and liability for certain taxes. Historians have often connected the decree with the expansion of the tax base, particularly inheritance taxation, although its precise motivation is uncertain.
The grant did not erase every social distinction. Slavery continued, local customs remained important, and elite status still varied greatly. The decree nevertheless changed the legal framework of the empire by making citizenship far more universal than it had been during the Republic or early imperial period.