Marija Lešaja was born in Zagreb in 1983. She attended the Blagoje Bersa School of Music, where she studied the flute (Prof. Vesna Hajdin) and singing (Prof. Viktorija Badrov). After studying philosophy and sociology she attended the Music Academy in Zagreb where she graduated in the class of Associate Professor Cynthia Hansell-Bakić. In 2008 she started a two-year Master’s Study at the University of Music and Performing Arts in Vienna in the class of Prof. Theimer and Prof. Orlowsky. She attended seminars by Olivera Miljaković, Dunja Vejzović, Rotraud Hansmann, Georg Nigl, Gerhard Zeller, Neda and Željka Martić. During her studies in Zagreb she won several awards at county competitions and an award at the state competition. She is also the recipient of the Rector's Award for participation in the "L’elisir d’amore" project in 2008. In 2010 she was one of the finalists of the Nico Dostal International Operetta Competition in Austria. During her studies she performed as a soloist with the Zagreb Philharmonic Orchestra and with the orchestra and choir of the Music Academy. She has appeared in the roles of Gretel in Hansel and Gretel, Melpomene in Il Parnaso confuso (Schlosstheater Schoenbrunn Vienna), Euridice in Orfeo ed Euridice (Probebuehne- Mdw Vienna), Ida in Die Fledermaus, Papagena in Die Zauberfloete, Barena in Jenufa, Čobanče in Ero the Joker, and Berta in Il Barbiere di Siviglia (Croatian National Theatre in Zagreb). She has performed as a soloist with Vjekoslav Šutej, Uroš Lajovic, Nikša Bareza, Tomislav Fačini, Igor Vlajnić, Josip Šego, Srboljub Dinić, as well as with the Croatian Military Orchestra, the Zagreb Philharmonic Orchestra, the Rijeka Opera Orchestra and the Music Academy Orchestra. She has appeared at the Chamber Music Festival in Vukovar, the Evenings of St. Donat, the Peter Nakić Organ Festival in Rab, in a live broadcast of Croatian Radio at the Salon Očić, the Rovinj Festival, the Festival of Organ Heferer, the Passion Heritage Festival, the Christian Culture Festival, the Showroom of Contemporary Sound, the Festival of Organ Music in the Lika-Senj County, the Korčula Summer of Culture, the Blato Music Festival, the Omiš Summer of Culture, etc. She has held four recitals in Vienna, organized by Matica Hrvatska in Vienna and the Austrian-Croatian Society in Vienna. She has performed the music of W. A. Mozart and R. Strauss with the Salon Orchestra Alt-Wien in Vienna. She has given numerous concerts in Austria with the Vienna Kuenstlerforum, where she performed an operetta and Wienerlied. She has also appeared as a soloist in the premiere of the musical suite for ensemble and soprano by Mirela Ivičević Planet 8 alias Operation Neptune in Theatre ITD, which won the J. Š. Slavenski award for the best musical work in 2013.
She has performed at the Music Salon SC’s Showroom of Contemporary Sound in 2014 and with Hilary Jeffrey’s experimental ensemble in 2015. She performed as a soloist with the Cantus ensemble, when she sang M. Belamarić’s 5 Poemas de Cante Jondo. She has performed several times with the ensemble of Glazbene staze. She regularly collaborates with organist Katarina Javora with whom she gave numerous recitals of sacred and baroque music. She has performed renaissance music with the Minstrel
ensemble. Since 2013 she is a member of the Le Trio ensemble with Eda Rimanić and Iva Ljubičić with whom she performs French music spanning from romanticism to contemporary music. She has performed J. Cage's Aria for solo voice at the Museum of Contemporary Art in Zagreb.
She recorded a couple of radio plays for Croatian radio. She has been a member of The Croatian Society of Music Artists (HDGU) and Kuenstlerforum from Vienna since 2011.

As of 2017 she is a member of the Croatian Freelance Artists Association. That same year she performed in Vienna Peterskirche and Music Biennale Zagreb in a premiere of Frog the Queen, composed by Sara Glojnarić and directed by Rene Medvešek.

In the year 2018 she performed F. Poulenc's La voix humaine in Scena Ribnjak in Zagreb and HNK Varažadin.

Both in 2017 and 2018 she was a part of project Biljke i svirke with pianist Kosjenka Turkulin.