Lárus Halldór Grímsson (born December 13, 1954) is an Icelandic composer and musician. He is known mostly for his electronic compositions with traditional instruments but he has been writing more non-electronic works since 1990.

He began studying at the Reykjavík College of Music in 1971. There he concentrated mostly on the flute, but also learned to play keyboards. He played on both instruments with several bands in the 1970s, the most famous being Eik (1974-1979).

In 1979 he began studies at the Institute of Sonology (Instituut voor Sonologie) in Utrecht, in the Netherlands. After finishing his studies there in 1984, he worked at the institute for quite some time.

Lárus has worked with many of Iceland's most famous and talented artists. He currently runs the Skólahljómsveit Vesturbæjar og Miðbæjar music school and wind band for children, in addition to conducting the Reykjavik City Band (Lúðrasveit Reykjavíkur).