Ruut Tarmo (April 26, 1896 – January 28, 1967) was an Estonian stage and film actor and stage director whose career spanned more than five decades.

Ruut Tarmo was born Harald Rudolf Klein in Tartu in 1896 to Julius Klein and Sohvi Klein (née Anja) and he began his career on stages in his hometown in 1912. In 1914 he began an engagement at the prestigious Vanemuine Theatre and would later travel the world's stages (including at least two appearances on London stages with fellow countryman Ants Eskola), as well as at the Estonian National Opera and the Estonian Drama Theatre. In 1927 he would make his film debut in the Aksella Luts and Theodor Luts-penned and directed silent film drama Noored kotkad (English: Young Eagles), which chronicled Estonian soldiers fighting in the Estonian War of Independence from 1918 to 1920