The concepts of security sector governance and reform (SSG/R, or SSG and SSR) generally refer to a process in Western-based international development and democratization to amend the security sector of a state towards good governance and its principles, such as freedom of information and the rule of law. The security sector governance and reform can be part of international development or democratization. The objective of security sector reform (SSR) is to achieve good security sector governance (SSG)—where security actors are effective and accountable to their people. For example, SSR might guide decision-making on what form should the oversight of armed forces take or how transparent will intelligence agencies be according to legislation. Different nomenclature of the same overall framework include security system reform (SSR), security sector reconstruction (SSR) and justice and security sector reform (JSSR).

In 1994, the Organization for Security and Co-operation in Europe (OSCE) adopted a Code of Conduct on Politico-Military Aspects of Security stating that the democratic control of the security sector as essential to stability.

The framework emerged after Saferworld staff observed from examples in South Africa, Indonesia and countries in Eastern Europe that national security and its components were considered crucial in a state recovering from conflict or an authoritarian regime. On 13 May 1998, Clare Short, Secretary of State for International Development, used the term for the first time, publicly, during a speech at the Royal College of Defence Studies. Reportedly, the increasing number of civil wars led development actors to look at the problem of insecurity from the perspective of good governance. The conclusion was that the security sector should adhere to the same rules of good governance as any other public service to curb conflict and violence.

In 2014, the United Nations Security Council (UNSC) adopted its first stand-alone resolution on SSR and within it the role of security sector reform in stabilizing post-conflict countries.

There is no single globally accepted definition of security sector reform (SSR), but it generally refers to a process to reform or rebuild a state's security sector towards good security sector governance (SSG). Good SSG is usually defined as a number of idealized principles and good practices of a healthy security sector servicing its people. Likewise, the objective of SSR is defined as the application of the same principles of good governance to the security sector as to any other public sector service delivery, such as public health or education. For example, the Development Assistance Committee (DAC) of the Organisation for Economic Co-operation and Development (OECD) has defined four standards that SSR should strive for:

1. Establishment of effective governance, oversight and accountability in the security system; 2) improved delivery of security and justice services; 3) development of local leadership and ownership of the reform process; and 4) sustainability of justice and security service delivery.

The target of SSR are the components of the state that uphold national security. Although the security sector is therefore a wide term open to interpretation, it is generally used to describe the structures, institutions and personnel responsible for the management, provision and oversight of security in a certain country. Therefore, the scope and target of SSR has usually been defined comprising the following two groups:

To observe and measure the quality of SSG as well as set more definite objectives, international development actors generally break down good security sector governance into different principles that are believed to showcase different subparts of a healthy security sector under democratic control. While exact configurations vary, some of the most common principles or objectives of good SSG that are commonly used include accountability, rule of law, and effectiveness. Political bias can show in the security sector.