SO1

SO1 may refer to:
 * Specialist Protection Command a command division within the Specialist Operations Directorate of London's Metropolitan Police Service
 * Special Operator: Naval Special Warfare, SEAL; see United States Navy SEALs
 * Sonarman First Class, a former American naval rank.
 * A staff officer of the first class, usually an officer of commander, lieutenant colonel or wing commander rank.
 * Special Operations 1 - Propaganda, of SOE (Special Operations Executive, British, World War II)