Phraya Tani (Thai: พญาตานี) or Seri Patani (Malay) is a 17th century siege cannon from Pattani Province in southern Thailand. It is the largest cannon ever cast in what is now Thailand, measuring 9 feet long and made of brass. It is on display in front of the Ministry of Defence, opposite the Grand Palace in Bangkok. The cannon still serves as the symbol of Pattani Province.
The Phaya Tani was cast in the early 17th century by a craftsman of Chinese origin named Tok Kayan. The then ruler of Sultanate of Pattani, Raja Biru, ordered the construction of powerful artillery in response to rumors of a forthcoming attack from Siam. Three cannon were cast, two siege guns known as the Seri Patani and Seri Negara, and a smaller cannon named the Mahalela.
After the fall of Ayutthaya to the Burmese in 1767, the Sultanate of Pattani renounced its tributary status to Siam and declared its complete independence. Eighteen years later, however, a Thai army led by King Rama I's brother, the vice-king Boworn Maha Surasinghanat, invaded and conquered Patani. The Seri Patani and Seri Negara were ordered to be sent to Bangkok as spoils of war. The Seri Negara came loose as it was being loaded aboard a ship and plunged into the sea, where it rests to this day.