Kaasik is an Estonian surname (meaning birch forest). Notable people with the surname include:
Ain-Elmar Kaasik (1934–2026), Estonian neurologist, neurosurgeon and academic Gert Kaasik, Estonian-born Finnish rapper and DJ Hannes Kaasik (born 1978), Estonian football referee Tõnis Kaasik (born 1949), Estonian entrepreneur, fencer, environmentalist, conservationist, and politician Ülo Kaasik (1926–2017), Estonian mathematician
See also Kaasiku (disambiguation), several villages in Estonia Kasemets, Estonian surname also meaning birch forest