Organización Obreira
Organización de Telecomunicaciones de Iberoamérica
Organización Radial Olímpica
Organización Editorial Mexicana
Organización Médica Colegial de España
Organización Ardila Lülle
Workers' Revolutionary Organization (Spain)
Organisation of Marxist–Leninists of Spain
Organizacion Corona
Bases y puntos de partida para la organización política de la República Argentina
ODESUR
Organization of Communist Left
Organization of People in Arms
Organization for the Liberal Democracy in Venezuela
Islamic Organization of Latin America
Anarchist Organization of the Spanish Region
Organización Primero de Marzo
Organización de Trabajadoras Sexuales
ONCE
Communist Organization of Spain (Red Flag)
José Martí Pioneer Organization
Nationalist Democratic Organization
Organizacion de Narcotraficantes Unidos
Organization of Revolutionary Unity
Autonomous Galician Republican Organization
Workers' Socialist Organization
Soriana
EOI Business School
Organization of Ibero-American States
National Transplant Organization
Copei
Organización Nacional Estudiantil de Fútbol Americano
Organization of American States
Organization of Solidarity with the People of Asia, Africa and Latin America
Central American Integration System
O&M College
El Yunque (organization)
World Trade Organization
Freedom Road Socialist Organization
United Nations
World Organisation for Animal Health
World Health Organization
Los Freddy's
Food and Agriculture Organization