Urmas Sisask (born September 9, 1960) is an Estonian composer.

One of the major inspirations for his music is astronomy. Based on the trajectories of the planets in the solar system, he created the planetal scale , a mode consisting of the notes C#, D, F#, G#, and A. Later, he discovered to his surprise that this was exactly the same as the Japanese Kumayoshi mode.

He is a Roman Catholic, and a large part of what he writes is sacred music.

Some of his works

• Starry Sky Cycle (Estonian: "Tähistaeva tsükkel") (1980-1987)
• Gloria Patri (1988)
• Pleiads ("Plejaadid") (1989)
• Milky Way ("Linnutee galaktika") (1990)
• Andromeda ("Andromeda galaktika") (1991)
• Christmas oratorio ("Jõuluoratoorium") (1992)
• Magnificat
• Missa Nr. 1
• Symbiotic Symphony ("Sümbiootiline Sümfoonia")
• Comet Hyakutake
• Ave Sol
• Missa Nr. 4 op. 46: Christmas mass ("Joulumissa")
• Polaris ("Pohjanael")