Wat Phra Si Rattana Mahathat, or Wat Yai, is a revered Buddhist temple in Phitsanulok Province, Thailand. Founded in 1357 by King Lithai of Sukhothai, it is renowned for housing one of the most beautiful Buddha images in the country, the Phra Phuttha Chinnarat. The temple's rich history is marked by royal patronage and artistic evolution, reflecting the changing styles of successive Thai kingdoms. It stands as a testament to the spiritual and cultural heritage of Thailand, attracting devotees and historians alike.