Nithyasree Mahadevan, also referred to as S. Nithyashri Mahadevan (born August 25, 1973) is an eminent Indian classical musician and playback singer for film songs in many Indian languages.

Nithyasree, was born to Lalitha Sivakumar and Injikudi Sivakumar. Her mother Lalitha Sivakumar, who was Palghat Mani Iyer's daughter and learnt Carnatic music from her mother-in-law (Nithyasree's grandmother), D. K. Pattammal, was Nithyashree's first guru (teacher).

Nithyashree would, like her mother, learn from her grandmother, D. K. Pattammal, as well as accompany her in concert. Nithyashree's father would constantly show his support, as he being an accomplished mridangist, would be Nithyashree's accompanist whenever he can. Nithyashree's commanding, high-pitched voice is well suited to carnatic music, devotional, patriotic and popular songs. Her amazing voice, coupled with her style and vast repertoire, impresses audiences all over the world.

Nithyashree and her husband, Mahadevan, have 2 daughters, Tejashree and Tanujasree.

Nithyashree's introduction to playback singing came when A.R. Rahman called her to Panchathan Recording Inn, in Chennai, for a voice test. The output from her visit became a huge hit, and was used in the movie "Jeans" starring Aishwarya Rai. After this, Nithyashree was in demand for playback singing for films and drama serials.

Nithyashree's first maiden Carnatic performance was for the Youth Association For Classical Music on 10th August 1987, in which she was titled 'best concert of the series'. She is an A.I.R. Prize Winner (1990) and has been an 'A' grade artist. She has been awarded the "Yuva Kala Bharathi" title by Bharath Kalachar in 1994, "Innisai Maamani" by Tamil Nadu Welfare Association, and various other prestigious awards such as "Kalaimamani", "Isai Paeroli" (2001). She has received "Best Concert Award" from The Music Academy during the music festivals a couple of times and has also performed for the "Sangeeth Natak Academy" twice in their International Music Festivals in Bombay and Hyderabad.

She has performed in all major sabhas all over India and has presented her concerts in the United States of America, Canada, United Kingdom, Australia, United Arab Emirates, Germany, Singapore, Malaysia and various other destinations throughout the world.

She has presented a paper on the Life and Contribution of Gopalakrishna Bharathi for the Music Deparment of PSG College, Coimbatore and made two thematic albums popularising a number of Gopalakrishna Bharathi 's compositions. Nithyasree has also given a Lecture Demonstration in Coimbatore for Manoranjitham on "Papanasam Sivan - A Legend" and likewise, released a couple of thematic albums popularising compositions of Papanasam Sivan. She received the "Best Promising Artiste" from "Mohanam" Music Club, and made a thematic album of compositions popularising the Ragam Mohanam. She has given numerous concerts consisting of only patriotic songs to commemorate the 50th year of Indian Independence, a few with her grandmother D. K. Pattammal while her grandmother was still performing. Similarly, Nithyashree released a few albums popularising patriotic songs.