Sinhala: එම් ඒ සුමන්තිරන්, romanized: M A Sumanthiran) born 9 February 1964) is a Sri Lankan Tamil lawyer and politician.

[4] He has appeared in a number of fundamental rights cases and judicial reviews of parliamentary legislation and executive action including the charging of levy for water and establishing a revenue authority.

[4] He prevented the forced expulsion of Tamils from Colombo and successfully challenged an anti-conversion bill which the courts struck down as being unconstitutional.

[4][8] He has also appeared for petitioners against the proposed 18th and 19th amendments to the constitution which were found to be unconstitutional and required two-thirds majority in Parliament and a referendum.

[4][9] He has worked on a number of public interest cases including the ongoing attempt by residents of the Valikamam North High Security Zone to get their land back from the Sri Lankan military.

[4] His human rights work has led to him being threatened, harassed and branded "traitors in black coats" by the Sri Lankan military under the then President's brother Gotabhaya Rajapaksa.

[26][27] In January 2017 the Sri Lanka Police's Terrorist Investigation Department (TID) arrested several former members of the militant Liberation Tigers of Tamil Eelam (LTTE) in connection with the attempted assassination of Sumanthiran.

[38][39][40] The preferential vote count held at Jaffna Central College on 6 August 2020 was marred by violent clashes between supporters of various candidates from various parties.