Sedapatti R. Muthiah (4 October 1945 – 21 September 2022) was an Indian politician of the Dravida Munnetra Kazhagam. He was one of the leaders of the All India Anna Dravida Munnetra Kazhagam (AIADMK) from its creation and was second in command in AIADMK until 1998. He was popularly known by the name Sedapattiar. He remained a popular politician in Madurai district and had a mass support base in T.Kallupatti Union.

Muthiah was born in the small village of Muthappanpatti 5 km from T. Kallupatti. He was a post-graduate (M.Sc.) in Mathematics with Distinction from Thiyagarajar College, Madurai. Muthiah wanted to pursue Engineering after his PUC. Since he was from a rural background, he did not get admission into engineering college. He was into academics before moving into politics.

R. Muthiah entered politics as Student Leader in Dravida Munnetra Kazhagam (DMK) in the early days of Dravidian Movement. He took part in the anti-Hindi agitations. He was also a good orator in Tamil. When M.G.R. started AIADMK a lot of his supporters left DMK and joined AIADMK. Muthiah along with his supporters joined as well given the fact that M.G.R. had a major support in Madurai Region. In fact Muthiah was the first choice of M.G.R. to contest from Dindidul constituency for the party's first election campaign since its inception in 1973. Due to some reasons, the chance went to Maya Thevar.

Muthiah was chosen to stand from Sedapatti constituency under which hometown comes based on the support he had as a Student Leader in 1977. He won the elections and got elected to the Legislative Assembly. He went on to win consecutive elections from Sedapatti. He was made the Speaker of the Assembly in 1991 and continued his tenure till 1996. Due to his continued victory in all elections he became a household name of the region and hence was fondly called as "Sedappattiyar" by people of the area, which later became his name. During his time T.Kallupatti transitioned itself from a sleepy small village into a Town Panchayat administering 42 villages.

He was elected as a Member of Parliament twice from Periyakulam Constituency for Ninth Lok Sabha and Twelfth Lok Sabha. In the Twelfth Lok Sabha he served as a Union Minister for Surface Transport in Atal Bihari Vajpayee cabinet.^[1] He was in the post for a short period of time and had to resign due to a case in Chennai court. He graciously resigned from the post and faced the charges for the 42 lakh case.^[2] Political critics say DMK was behind the case. His resignation is a rare occurrence comparing the scams of recent years of very large proportion. He then served as Leader of AIADMK in the parliament and raised issues concerning people.

M. Manimaran, younger son of Sedapatti Muthiah is currently the Secretary of Madurai South District, DMK party. Sedapatti Muthiah's popularity and Manimaran's recent performance along with the larger families in nearby villages and Mukkulathor community has gained him fame. He also contested from Thirupparankundram constituency in 2016 State Elections but lost.^[8]

He died in Madurai on 21 September 2022, at the age of 76.^[9]