The Melbourne Symphony Orchestra (MSO) is an orchestra based in Melbourne, Australia. It has 100 permanent musicians. Melbourne has the longest continuous history of orchestral music of any Australian city and the MSO is the oldest professional orchestra in Australia. The MSO performs to more than 250,000 people in Melbourne and regional Victoria in over 150 concerts a year.

Following integration with the Melbourne Chorale in 2008, the Orchestra has responsibility for its own choir, the MSO Chorus.