Collective security is a multi-lateral security arrangement between states in which each state in the institution accepts that an attack on one state is the concern of all and merits a collective response to threats by all. Collective security was a key principle underpinning the League of Nations and the United Nations. Collective security is more ambitious than systems of alliance security or collective defense in that it seeks to encompass the totality of states within a region or indeed globally.

सामूहिक सुरक्षा से आशय ऐसी क्षेत्रीय या वैश्विक सुरक्षा-व्यवस्था से है जिसका प्रत्येक घटक राज्य यह स्वीकारता है कि किसी एक राज्य की सुरक्षा सभी की चिंता का विषय है। यह मैत्री सुरक्षा की प्रणाली से अधिक महत्वाकांक्षी प्रणाली है।