The Temple of the Emerald Buddha or Wat Phra Kaew is a royal chapel situated within the walls of the palace. Incorrectly referred to as a Buddhist temple, it is in fact a chapel; it has all the features of a temple except for living quarters for monks. Built in 1783, the temple was constructed in accordance with ancient tradition dating back to Wat Mahathat, a royal chapel within the grounds of the royal palace at Sukhothai, and Wat Phra Si Sanphet at Ayutthaya. The famed Emerald Buddha is kept within the grounds of the temple.

The temple is surrounded on four sides by a series of walled cloisters, with seven different gates. Like those ancient royal temples of Sukhothai and Ayutthaya, the Wat Phra Kaew complex is separated from the living quarters of the kings. Within these walls are buildings and structures for diverse purposes and of differing styles, reflecting the changing architecture during the various reigns of the kings. Despite this, most of the buildings within adhere strictly to classical Thai architecture. The establishment of the Temple of the Emerald Buddha dates to the very founding of the Grand Palace and Bangkok itself.

The Emerald Buddha is an image of the meditating Gautama Buddha seated in the lotus position, made of a semi-precious green stone, clothed in gold and about 66 centimetres (26 in) tall. The image is considered the sacred palladium of Thailand. It is housed in the Temple of the Emerald Buddha (Wat Phra Kaew) on the grounds of the Grand Palace in Bangkok.

Historical sources indicate that the statue surfaced in northern Thailand in the Lan Na kingdom in 1434. One account of its discovery tells that lightning struck a chedi in Wat Pa Yia (Bamboo Forest Monastery, later renamed Wat Phra Kaew) in Chiang Rai, revealing a Buddha covered with stucco inside. The Buddha was then placed in the abbot's residence, who later noticed that stucco on the nose had flaked off, revealing a green interior. The abbot removed the stucco and found a Buddha figure carved from a green semi-precious stone, which became known as Phra Kaew Morakot or in English the Emerald Buddha. ("Emerald" refers to its "green colour" in Thai, not its composition.)[5][6] Some art historians describe the Emerald Buddha as belonging to the Chiang Saen Style of the 15th century CE, which would mean it is of La Na origin.

The legend reports that King Sam Fang Kaen of Lan Na wanted it in his capital, Chiang Mai, but the elephant carrying it insisted, on three separate occasions, on going instead to Lampang. This was taken as a divine sign, and the Emerald Buddha stayed in Lampang in a specially-built temple (now Wat Phra Kaeo Don Tao) for the next 32 years. In 1468, it was moved to Chiang Mai by King Tilokaraj, where it was kept in a niche in a large stupa called Chedi Luang.[7]

The Emerald Buddha remained in Chiang Mai until 1552, when it was taken to Luang Prabang, then the capital of the Lao kingdom of Lan Xang. Some years earlier, the crown prince of Lan Xang, Setthathirath, had been invited to occupy the vacant throne of Lan Na.

In 1564, King Setthathirath moved it to Vientiane, which he had made his new capital due to Burmese attacks and where the Buddha image was housed in Haw Phra Kaew. The Buddha image would stay in Vientiane for the next 214 years.

In 1779, the Siamese General Chao Phraya Chakri put down an insurrection, captured Vientiane and took the Emerald Buddha to Siam. It was installed in a shrine close to Wat Arun in Thonburi, the new capital of Siam. Chao Phra Chakri then seized the throne for himself and founded the Chakri Dynasty of the Rattanakosin Kingdom, where he would later be titled King Rama I. He shifted his capital across Chao Phraya river to its present location in Bangkok, and constructed the new Grand Palace including Wat Phra Kaew within its compound. Wat Phra Kaew was consecrated in 1784, and the Emerald Buddha was moved with great pomp and pageantry to its current home in the ubosot of the Wat Phra Kaew temple complex on 22 March 1784.