Banyat Bantadtan (林書清) (Thai: บัญญัติ บรรทัดฐาน; RTGS: Banyat Banthatthan, born 15 May 1942) is a Thai politician. From 2003 to 2005, he was the chairman of the Democrat Party and Leader of the Opposition against Prime Minister Thaksin Shinawatra.

Banyat Bantadtan was born in Kanchanadit, Surat Thani Province. A lawyer by training, he holds a Bachelor of Laws from the Faculty of Law, Thammasat University. In 1970, he became a lecturer for the Office of Accelerated Rural Development (ARD). In 1975, he was elected Member of Parliament for the first time. He was consistently re-elected in all subsequent elections until 2007.

Banyat was spokesman of the Democrat Party from 1979 to 1980. He was a cabinet member in the governments of General Prem Tinsulanonda, as deputy interior minister from 1980 to 1983, Minister in the Office of Prime Minister from 1983 to 1986, and as Minister of Science from 1986 to 1988. Under his fellow party member Prime Minister Chuan Leekpai, Banyat was Deputy Prime Minister from 1992 to 1995 and again in 2000, when he additionally led the Ministry of Interior.

In 2003, he succeeded Chuan as chairman of the Democrat Party and became official Leader of the Opposition. He stepped back after the electoral setback in 2005. The Thai Rak Thai Party of Prime Minister Thaksin Shinawatra had won the election by a landslide. The party chose Abhisit Vejjajiva as his successor.

Banyat was married to Somnuk Boonchu and they had one child, then were divorced. After the divorce he married Jittima Sangkasap (Thai: จิตติมา สังขะทรัพย์) ex-wife of Pongpol Adireksarn. They have two children.