The Ayutthaya Kingdom (ɑːˈjuːtəjə; อยุธยา, , IAST: or , ʔā.jút.thā.jāː), the Empire of Ayutthaya (1569–1767), or the Ayutthaya Empire, was a Siamese kingdom that existed in Southeast Asia from 1351 to 1767, centered around the city of Ayutthaya, in Siam, or present-day Thailand. European travellers in the early 16th century called Ayutthaya one of the three great powers of Asia (alongside Vijayanagar and China). The Ayutthaya Kingdom is considered to be the precursor of modern Thailand, and its developments are an important part of the history of Thailand.
The Ayutthaya Kingdom emerged from the mandala/merger of three maritime city-states on the Lower Chao Phraya Valley in the late 13th and 14th centuries (Lopburi, Suphanburi, and Ayutthaya). The early kingdom was a maritime confederation, oriented to post-Srivijaya Maritime Southeast Asia, conducting raids and tribute from these maritime states. After two centuries of political organization from the Northern Cities and a transition to a hinterland state, Ayutthaya centralized and became one of the great powers of Asia. From 1569 to 1584, Ayutthaya was a vassal state of Taungoo Burma, but quickly regained independence. In the seventeenth and eighteenth centuries, Ayutthaya emerged as an entrepôt of international trade and its cultures flourished. The reign of Narai ( () 1657–1688) was known for Persian and later, European, influence and the sending of the 1686 Siamese embassy to the French court of King Louis XIV. The Late Ayutthaya Period saw the departure of the French and English but growing prominence of the Chinese. The period was described as a "golden age" of Siamese culture and saw the rise in Chinese trade and the introduction of capitalism into Siam, a development that would continue to expand in the centuries following the fall of Ayutthaya.
Ayutthaya's failure to create a peaceful order of succession and the introduction of capitalism undermined the traditional organization of its elite and the old bonds of labor control which formed the military and government organization of the kingdom.