Mari Lill (born December 21, 1945) is an Estonian stage, film and television actress whose career began onstage in the late 1960s.

Mari Lill was born in Tallinn to Felix Lill and Asta Lill (née Multer) just after the end of World War II and the Soviet occupation and annexation of Estonia. Her father Felix was arrested by Soviet authorities and spent several years sentenced to forced labor in the gulag system in Siberia when she was still an infant. He was later able to return to the family when Mari was quite young. Lill is the middle child of three siblings; she has an older sister Kadri, and her younger brother was glass artist Ivo Lill. Lill grew up and attended schools in the district of Nõmme and spent time visiting her grandmother on the island of Saaremaa.

After graduating from secondary school, Lill studied acting under the supervision of course instructor Voldemar Panso at the Tallinn State Conservatory (now, the Estonian Academy of Music and Theatre). Her diploma production was in the role of Helen Keller in a 1967 staging of William Gibson's The Miracle Worker. She graduated in 1968. Among her graduating classmates were actors Helle-Reet Helenurm, Katrin Karisma, Raivo Trass, Enn Klooren, Jaan Tooming, Peeter Jakobi, and Kalju Komissarov.