Phra Nakhon Si Ayutthaya (or Ayutthaya, Thai: พระนครศรีอยุธยา, pronounced [pʰráʔ náʔkʰɔ̄ːn sǐː ʔājúttʰājāː]) is one of the central provinces (changwat) of Thailand. Neighboring provinces are (from north clockwise) Ang Thong, Lop Buri, Saraburi, Pathum Thani, Nonthaburi, Nakhon Pathom and Suphan Buri.

The name Ayutthaya derives from the Ayodhya of the Ramayana epic.