Ottakarathevar Panneerselvam, popularly known as OPS (born 14 January 1951)[1] is an Indian politician and former Chief Minister of Tamil Nadu briefly in December 2016 and previously from 2001 to 2002 and again from 2014 to 2015.

His third term began following Jayalalithaa's death and ended 2 months later when Edappadi K. Palaniswami was selected as the Chief Minister by the party.

He obtained a Bachelor of Arts degree from Haji Karutha Rowther Howdia College in Uthamapalayam, Theni district.

In March 2002, he resigned as Chief Minister and Jayalalithaa was sworn in again after the Madras high Court overturned her conviction and she won a by-election from Andipatti assembly constituency.

He was again entrusted with the responsibility of being Chief Minister of Tamil Nadu on 29 September 2014 when Jayalalitha was convicted in the disproportionate assets case.

On 22 May 2015, he resigned as Chief Minister and Jayalalithaa was sworn in again after the Karnataka High Court acquitted her in the disproportionate assets case on 11 May 2015.

[21] On 17 August, Justice G. Jayachandran of the Madras High Court ruled the expulsion of Panneerselvam and the decisions of the AIADMK General Council as invalid.

[25] On 23 February 2023, the Supreme Court of India upheld the decisions of the AIADMK general council meeting held on 11 July 2022, and dismissed the petition of O. Panneerselvam challenging the previous order of the division bench, thus affirming unitary leadership under Edappadi K Palaniswami.

[4][5] On 28 March 2023, The Madras High Court ruled in favor of Edappadi K. Palaniswami and dismissed the petitions of O. Panneerselvam challenging the resolutions passed at the general council meeting held on 11 July 2022.

[28][29] On 19 January 2024, the Supreme Court of India refused to stay the August 2023 order of the division bench of Madras High Court which dismissed the petitions of O. Panneerselvam challenging the 11 July general council resolutions that led to the expulsion of O. Panneerselvam and his supporters from the party, saying the interference at this stage will "lead to huge chaos".

Five pages of the Reddy's Diary suggest alleged payments made to several AIADMK ministers, MLAs, and many others, amounting to more than ₹48 crore.