Robert Hunter (27 November 1792 – 7 September 1848) was a British merchant and unofficial diplomat in Siam during the reign of King Rama III.

The Hunters had exported tobacco from Virginia to France, an enterprise ended by the American War of Independence, and then turned to manufacturing glass, cotton and linen from their base in Neilston, southwest of Glasgow.

In July 1824, Rama III succeeded to the throne in Bangkok, and Hunter arrived in August, bearing the calculated gift of a thousand muskets for the new king.

[2] After speaking with the Phra Klang (Minister of the Treasury), Hunter was granted the right to trade with foreigners on behalf of the king and nobility, and he was permitted to live in Bangkok.

The king ordered a three-story construction erected on the west bank of the Chao Phraya River for Hunter's business and residence.

[3] He lived in the Kudi Chin community, initially owning a large floating house before moving into a Western-style building upon its completion in 1840.

He was known for his hospitality to Western visitors and would entertain them: often taking them sailing on his 30-ton cutter, Friends, going on shooting expeditions, playing cards, dining and drinking.

[6] In 1825, Hunter married a half-Portuguese, half-Siamese woman named Angelina Sap who was from a respected Portuguese family[7] and a descendant of Constantine Phaulkon, the 17th-century adventurer in Siam.

He aided Henry Burney's successful treaty mission in 1826, and the governor of Singapore later praised Hunter for a history of "infinite service in our negotiation with [Rama III]".

The Burney Treaty granted more trading privileges for all British merchants in Singapore, but Hunter & Hayes dominated the market in Bangkok.

Unsatisfied with his response, Hunter steamed Express to Calcutta, the headquarters of the East India Company, to petition for redress of his grievances with the king.

He claimed that Rama III had violated articles of the Burney Treaty of 1826, and he recommended the establishment of a British consul in Bangkok, appearance of gunships in the area and a renegotiation of the import duty.

The Governor-General of India took no action, however, agreeing with the judgments of his subordinates that any violations on the king's part owed to personal dispute with Hunter and were not instances of systematic breach.

"[48] During the unsuccessful treaty mission of James Brooke in 1850, Rama III cited Hunter's fractious behavior as a reason for rejecting the terms for freer residence of Europeans.