| RSO | Radiation Safety Officer 
| Others |
| RSO | Radiation Safety Officers
| Others |
| RSO | Radiation Service Officer
| Others |
| RSO | Radiation Service Organization
| Others |
| RSO | Radiographic safety officer
| Others |
| RSO | Radiological Safety Office
| Others |
| RSO | Rainbow Service Organization
| Others |
| RSO | Rally Sport Omologato
| Others |
| RSO | Rally Sport Ontario
| Others |
| RSO | Range Safety Officer
| Others |
| RSO | Rapid Scan Operation
| Others |
| RSO | Rapid Specification Option
| Others |
| RSO | Reality Sports Online
| Others |
| RSO | Rear Seat Occupancy Alarm
| Others |
| RSO | Recognized Security Organization
| Others |
| RSO | Recognized Service Organization
| Others |
| RSO | Recognized Service Organizations
| Others |
| RSO | Recognized Student Organization
| Others |
| RSO | Recognized Student Organizations
| Others |
| RSO | Reconnaissance and Surveillance Operation
| Others |
| RSO | Reconnaissance Systems Officer
| Others |
| RSO | Rectified Skew Orthomorphic
| Others |
| RSO | Refinery Safety Overview
| Others |
| RSO | Regimental Supply Officer
| Others |
| RSO | Regina Symphony Orchestra
| Others |
| RSO | Regional Sales Office
| Others |
| RSO | Regional Security Officer
| Others |
| RSO | Regional Sub Office
| Others |
| RSO | Regional Support Office
| Others |
| RSO | Regional Support Organization
| Others |
| RSO | Regionalny System Ostrzegania
| Others |
| RSO | Registered Safety Officer
| Others |
| RSO | Registered Service Organization
| Others |
| RSO | Registered Student Organization
| Others |
| RSO | Registered Student Organizations
| Others |
| RSO | Remote Shared Object
| Others |
| RSO | Remote Spool Output
| Others |
| RSO | Remote Switch Operator
| Others |
| RSO | Rent Stabilization Ordinance
| Others |
| RSO | Resident Services Office
| Others |
| RSO | Resident Surgical Officer
| Others |
| RSO | Retirement Services Office
| Others |
| RSO | Retirement Services Officer
| Others |
| RSO | Revised Statutes of Ontario
| Others |
| RSO | Rick Simpson Oil
| Others |
| RSO | Ridiculously Showing Off
| Others |
| RSO | Right superior oblique
| Others |
| RSO | RIMCO Support Office
| Others |
| RSO | Road Safety Observatory
| Others |
| RSO | Road Safety Officer
| Others |
| RSO | Road Safety Organization
| Others |
| RSO | Roanoke Symphony
| Others |
| RSO | Roanoke Symphony Orchestra
| Others |
| RSO | Robert Stigwood
| Others |
| RSO | Robert Stigwood Organisation
| Others |
| RSO | Robert Stigwood Organization
| Others |
| RSO | Rochester Student Organization
| Others |
| RSO | Rock S*** On
| Others |
| RSO | Rock Sh*t On
| Others |
| RSO | Rock Solid Organization
| Others |
| RSO | Rockford Symphony Orchestra
| Others |
| RSO | Roger & Sherry Olsen Livestock
| Others |
| RSO | Rough Stud Opening
| Others |
| RSO | Round, Square, and Oval
| Others |