RSO explained

RSO or R.S.O. may refer to:

Roles and titles

Range safety officer, a person responsible for the safe use of rocket vehicles
Radiation Safety Officer, a person responsible for the safe use of radiation and radioactive materials
Regional Security Officer, a Diplomatic Security Service Special Agent in charge of security at a US embassy
Regional Security Office, office in a US embassy or consulate for the Diplomatic Security Service
- Swedish: Riddare av Svärdsorden, Knight of the Order of the Sword Reconnaissance systems officer, operator of surveillance systems and equipment on a Lockheed SR-71 Blackbird aircraft

Rohingya Solidarity Organisation, a political organization and former insurgent group in Myanmar (Burma)

Railway Sub Office (1855–1905), a British Royal Mail office which received mail directly from rail transport
Reactive Search Optimization, problem-solving methods with integrated online machine-learning capabilities
Revised Statutes of Ontario, the provincial laws of Ontario, Canada
Registered sex offender, a person listed on a sex offender registry
Republic of South Ossetia, a separatist organization in Georgia
Resident Space Object, any man-made object in Earth orbit no longer used by anyone
RSO, musical duo consisting of American musician Richie Sambora and Australian musician Orianthi
Rick Simpson Oil, a form of cannabis concentrate
Red Star OS, also abbreviated as RSOS, is a North Korean operating system