The 1985 Thai military coup attempt was a military coup attempt against the government of Prem Tinsulanonda, by former Thai military leaders on 9 September 1985, but a counter-coup by Prem government in the morning led to surrender of the coup forces.

Prem Tinsulanonda was a Thai military officer, politician, and statesman who served as the Prime Minister of Thailand from 3 March 1980 to 4 August 1988, during which time he was credited with ending a communist insurgency and presiding over accelerating economic growth. As president of the Privy Council, he served as Regent of Thailand from the death of King Bhumibol Adulyadej on 13 October 2016 until 1 December 2016, when Vajiralongkorn was proclaimed King. At the age of 98, Prem was the longest-living Thai Prime Minister. He is also the oldest regent of any country, surpassing Bavarian Prince Regent Luitpold's record, when he became the regent for king Rama X.