The Royal College Old Boys Association of NSW & ACT (RCOBA) is the alumni society (old boys’ association) established for the old Royalists living in NSW & ACT. RCOBA is affiliated to Royal College Union (RCU) founded in 1891. It is the oldest such alumni society in Sri Lanka.

RCOBA was set up to further the interests of the college and its past and present members, and to keep former pupils in touch with each other and with the school. Annually the RCOBA organizes many sporting and social events on behalf of its membership.

RCOBA has close links with all state based Old Boys Associations in Australia and also connected to broader RCU network around the world.