Giedrius Prunskus was born in 1971, Šiauliai. In 1978–1989 he attended the II secondary school in Jurbarkas. In 1985 he graduated from Jurbarkas Children Music School (violin). In 1989–1991 he studied at the Lithuanian Agricultural University, and in 1992–1995, at Kaunas Juozas Gruodis Conservatoire (Regina Kabalinienė, later Associated Professor Gediminas Šmitas singing class). He continued his solo singing studies at the Lithuanian Academy of Music and Theatre, Kaunas Faculty (Associated Professor G. Šmitas class). In 2000 he received his Bachelors degree. In 2001–2002 Prunskus studied at the ‘Felix Mendelssohn–Bartholdy’ College for Music and Theatre, Leipzig, Germany, under Prof. Jitka Kovařikova–Richter. Then he returned to continue his studies at the Lithuanian Academy of Music and Theatre, Kaunas Faculty, where he was awarded the Masters degree in 2003. In 2003–2005 Prunskus attended training classes at the Lithuanian National Opera and Ballet Theatre. Simultaneously, he was studying for art licenciate at the Lithuanian Academy of Music and Theatre; upon finishing his studies he was awarded the art licenciate qualification.
Since 2003 he has been working as an assistant at the Lithuanian Academy of Music and Theatre, Kaunas Faculty, Singing Department. In 2003, Prunskus joined the Lithuanian Musicians’ Union.

In 1999 and 2004 he participated in the International Jāzeps Vītols Singers Competition in Riga. In 2001, at the Stasys Baras Singers’ Competition, Vilnius, he won the first prize in the baritone category. In 1998–2001 Prunskus won the V. Baltrušaitis grant, which is usually awarded to the best baritone studying at the LAMT KF by way of competition.

G. Prunskus has been invited to LNOBT and Kaunas State Musical Theatre to sing various baritone parts (Germon in G. Verdi’s opera La Traviata, Valentine in Ch. Gounod’s Faust, Figaro in G. Rossini’s The Barber of Sevile, Radvila in B. Dvarionas’s opera Dalia, etc.). In 2000 he debuted at Kaunas State Musical Theatre with his part of Baron Douphal in G. Verdi’s La Traviata, and in 2004, at the Lithuanian National Opera and Ballet Theatre where he performed Camile’s part in F. Lehar’s operetta The Merry Widow.  Prunskus has been working together with Kaunas Philharmonic, Kaunas State Choir and various orchestras and choirs of the country. He often gives concerts as a soloist both in the country and abroad: Czech Republic, Germany, Poland, Switzerland and Estonia. Next to his opera repertoire, the singer also performs Lied genre music, oratories and religious music (Ch. Gounod’s Solemn Mass, C. Saint–Saëns’s Christmas Oratorio, Č. Sasnauskas’s Requiem, J. Haydn’s Requiem, etc.). He has been preparing theme solo concerts (F. Schubert’s vocal cycle Winterreise, J. Brahms’s vocal cycle Magelone, the concert of music by German composers From Bach to..., and the concert of music by Lithuanian composers, The Country I Grew Up in, etc.).