Wat Phra Mahathat was built during the reign of Borommaracha I (Boromma Rachathirat I) or Khun Luang Pa Ngua (1370- 1388), who was the third king of the Ayutthaya Kingdom.

Ayutthaya (Ayudhya)) was a Siamese kingdom that existed from 1351 to 1767. Ayutthaya was friendly towards foreign traders, including the Chinese, Vietnamese (Annamese), Indians, Japanese and Persians, and later the Portuguese, Spanish, Dutch and French, permitting them to set up villages outside the city walls. In the sixteenth century, it was described by foreign traders as one of the biggest and wealthiest cities in the East. The court of King Narai (1656??688) had strong links with that of King Louis XIV of France, whose ambassadors compared the city in size and wealth to Paris.