Ayutthaya was founded in 1350[a] by King U-Thong. However, the establishment of Ayutthaya is far older than 14th century. Evidence shown that the area was already populated during Mon Dvaravati period. Sources further mentioned that around 850 AD, the Khmers occupied the area and established a stronghold there, named it as Ayodhya after one of the holiest Hindu cities of India of the same name. Early history of Ayutthaya is historically connected to this Khmer settlement.[7][8] Consistently, Prince Damrong also agreed that there was a city called Ayodhya which was found by the Khmers ruling from Lopburi at the point where the three rivers meet.[9] Excavation map shows the traces from an ancient baray (water reservoir) close to the southwestern tip of Wat Yai Chai Mongkhon which could has been built on a former important Khmer temple complex.[10]
Ayutthaya was the capital of Thailand (then called Siam) for 417 years from 1350, until in Burmese–Siamese War (1765–1767), it was sacked by the Burmese army in 1767. During this era, now usually referred as the Ayutthaya period or Ayutthaya kingdom, Ayutthaya was ruled by 33 kings of five different dynasties. The kingdom became a major regional player, and a trade center of the East, a meeting point of European merchants and Asian traders. Notable monarchs during the Ayutthaya period include King Naresuan the Great, who liberated Ayutthaya from the first Burmese occupation and embarked on a reign of conquest, and King Narai the Great, who initiated diplomatic relations with France, during the reign of Louis XIV. His reign was the golden age of trade and culture.
The city was strategically positioned. During several months of the year, the flood plains around the cities would be flooded by the many rivers around the city. Enemy sieges were thus impossible, and forced to withdraw. This advantage was a contributing factor in the many failed Burmese invasions.