Riythvika Panneerselvam (also known as Riythvika Kasayam) is an Indian actress born on 5 August 1992 in Chennai, Tamil Nadu. She studied at Springfield Matriculation Higher Secondary School and Dr. K.K. Nirmala Girls' Higher Secondary School in Chennai, before graduating in BSc Physics from Justice Basheer Ahmed Sayeed College for Women (SIET), Teynampet, Chennai. She is the only member of her family in the film industry and would otherwise have pursued an IT career. She made her acting debut in director Bala's Paradesi (2013) as Karuthakanni, a role she landed after auditions while sending her portfolio to film PROs during college. She gained wide recognition for her pivotal role as a North Chennai girl in Pa. Ranjith's Madras (2014), earning the Filmfare Award for Best Supporting Actress - Tamil and multiple other nominations. She subsequently appeared in Kabali (2016) as a drug addict, Iru Mugan (2016) as a prostitute, Oru Naal Koothu (2016) as a radio jockey, Torchlight (2018), Onaaigal Jakkiradhai (2018), Sigai (2019), Irandam Ulagaporin Kadaisi Gundu (2019), Walter (2020), Navarasa (2021, Netflix), Cadaver (2022), and Yaavarum Vallavare (2024). In 2018, she participated in Bigg Boss Tamil Season 2, hosted by Kamal Haasan on Star Vijay, and emerged as the winner on 30 September 2018.

Tamil films Paradesi (2013, director Bala) as Karuthakanni; Madras (2014, Pa. Ranjith) for which she won the Filmfare Award for Best Supporting Actress - Tamil; Kabali (2016) opposite Rajinikanth; Iru Mugan (2016) opposite Vikram; Torchlight (2018); winner of Bigg Boss Tamil Season 2 (2018) with a ₹50 lakh prize.

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