Finnish cellist Petja Kainulainen (b.1983) has become known especially as a chamber musician in Finland and abroad.

He has studied cello and chamber music at the Sibelius Academy, the Britten-Pears School of Music, and the European Chamber Music Academy (ECMA).

With the Kamus Quartet, he has recorded the album Different Voices that won YLE's Record of the Year award, the album Homunculus thar won the Emma award for classical music, the album of Seppo Pohjola's string quartets 1-4, which was nominated for Emma, ​​the album Itämerelle, released in the summer of 2021, which was nominated for Emma in the spring of 2022 and YLE's album of the year nominee. The Kamus quartet performed all of Ludwig van Beethoven's string quartets as the Beethoven Effect concert series, and in 2022-2025 Kamus will record all the same quartets as a series of seven discs.

With the Kamus Quartet, he has given concerts widely in Finland and abroad. In 2011-2012, he performed a series of concerts including all of Beethoven's cello-piano and violin-piano sonatas with Emil Holmström and Pasi Eerikäinen in Kauniainen, Kuopio, and Porvoo.

Petja is a founding member of Jousia Ensemble and Tapiola Ensemble.

He also works as the artistic director of Mejn Festival with the Kamus quartet and the Kino Soi! concert series with Liina-Mari Raivola, Hanna Hohti, and Markus Hohti.

Together with the Kamus quartet, he also planned the Kuulkaa! Chamber Music Belongs To Everyone concert series,

the Teema@Helsinki concert series in 2014-2018 and the Hiljaisuuden Rikkominen concert series in 2017.

Since 2012, he has been a cello and chamber music lecturer at the Espoo College of Music, a teacher at the Sibelius Academy of the University of the Arts since 2018, and a cello and chamber music teacher at the Centria University of Applied Sciences since 2020.

Kainulainen plays on a Claude-Augustin Miremont (1883) cello kindly loaned by the Finnish Cultural Foundation. For 2024, the Central Committee of the Arts awarded Petja a 1/2-year music artist grant, and for 2016, a one-year music artist grant.