Gustav Ernesaks (December 12, 1908 – January 24, 1993) was an Estonian composer and a choir conductor.

Ernesaks was born in Perila, Peningi Parish. He played an integral role in the Singing Revolution and was one of the father figures of the Estonian Song Festival tradition. One of his songs, a setting of Lydia Koidula's poem Mu isamaa on minu arm, became an unofficial national anthem during the years of Estonian SSR. His performance of the song at the XVII Estonian Song Festival was one of the inspirations for Dmitri Shostakovich's 1970 a capella choral cycle, Loyalty. He dedicated the score to Ernesaks, who also premiered it in Tallinn. He also composed the Estonian SSR anthem used between 1945 and 1990.

In 1935, Ernesaks married Stella Merjam. They had three sons: Ott Ernesaks, Jüri Ernesaks and Peep Ernesaks. Stella died in 1973. Ernesaks died in Tallinn, aged 84. A statue of him was erected in 2004 on the Tallinn Song Festival Grounds.