The International Organization of Supreme Audit Institutions (INTOSAI) is an intergovernmental organization whose members are supreme audit institutions. Nearly every supreme audit institution in the world is a member of INTOSAI. Depending on the type of system used in their home country, the members of INTOSAI may be variously titled the Chief Financial Controller, the Office of the Comptroller General, the Office of the Auditor General, the Court of Accounts, or the Board of Audit.

INTOSAI holds a triennial conference entitled the International Congress of Supreme Audit Institutions (INCOSAI).^[2] It publishes the quarterly International Journal of Government Auditing and publishes guidelines and international standards on auditing.

INTOSAI was founded in 1953^[3] in Havana, Cuba.^[4] Thirty-four audit organizations formed the group originally and as of 2010 the current membership includes 193 institutions (188 national institutions, the European Court of Auditors and 4 associated members).^[3]

The members of INTOSAI are the primary external auditors of the United Nations.^[4] The UN's General Assembly appoints the UN Board of Auditors (3 members appointed for 6 years) among the INTOSAI member representatives.^[5]

The International Standards of Supreme Audit Institutions (ISSAI) are a benchmark for auditing public entities (External Audit Standards for public entities).

The "INTOSAI Auditing Standards" had been approved by the INCOSAI in 1998 and updated in 2001. In its strategic plan 2005–2010, the INTOSAI decided to "provide an up-to-date framework of professional standards", so the INTOSAI Professional Standards Committee decided to merge the existing and new INTOSAI standards and guidelines into a framework.

The framework comprises all documents endorsed by INCOSAI with the purpose of guiding the professional standards used by SAIs

The list of ISSAIs is in the table below:

• Auditing Standards (ISSAI-numbers of 3 digits) stipulate general principles and postulates for carrying out the audit work;
• Implementation Guidelines (ISSAI-numbers of 4 digits) give more detailed guidance, practical assistance to SAIs in implementing the Standards in their individual constituents.

Examples of its major publications are:

• Guidelines for Internal Control Standards for the Public Sector (1992 - The current text is the 2004 revision by the INTOSAI Internal Control Standards Committee, approved by the XVIIIth INCOSAI of October 2004. It has been subsequently integrated in the INTOSAI standards/guidances as "INTOSAI GOV 9100"). It relies upon the COSO's integrated framework for internal control (as stated in the preface), and uses the COSO's definition of Internal Control and IIA's definition of Internal Audit.
• Guidelines on Best Practice for the Audit of Privatizations, (1998)
• Guidance for Planning an Audit of Internal Controls for Public Debt, (2002)

In addition to the INTOSAI members (the Supreme Audit Institutions), the following intergovernmental organizations have adopted INTOSAI AS:

• Council of Europe
• European Communities
  • The European Court of Auditors performs its audits in accordance with the IFAC and INTOSAI Auditing Standards and Codes of ethics, in so far as these are applicable in the European Community context.^[6]
• European Centre for Medium-Range Weather Forecasts
  • Audit by two appointed Supreme Audit Institutions.
• European Space Agency
  • Audit by an Audit Board composed of Supreme Audit Institutions auditors.
• EUMETSAT
  • Audit by an appointed Supreme Audit Institution.
• International Criminal Police Organization
• North Atlantic Treaty Organization
• Organisation for Economic Co-operation and Development
  • Audit by a Supreme Audit Institution.
• The United Nations
  • The United Nations' Board of Auditors (the external audit of the UN) has adopted the ISAs^[7] (International Standards on Auditing). The Board is composed of three Supreme Audit Institutions chairmen, familiar with and usually using the INTOSAI Auditing Standards.^[8]

The Institute of Internal Auditors (IIA) is among the five associated members of the INTOSAI.^[9] The INTOSAI is a strong advocate for the establishment of Independent Internal audit in public entities.

• ISSAI 1610 – Using the Work of Internal Auditors
• INTOSAI Guidance for Good governance: INTOSAI GOVs 9100–9230

The guidance "INTOSAI GOV 9100" states:

• (page 46) "The Supreme Audit Institution also has a vested interest in ensuring that strong internal audit units exist where needed. Those audit units constitute an important element of internal control by providing a continuous means for improving an organisation's operations. In some countries, however, the internal audit units may lack independence, be weak, or be non-existent. In those cases, the SAI should, whenever possible, offer assistance and guidance to establish and develop those capacities and to ensure the independence of the internal auditor's activities."
• "The creation of an internal audit unit as part of the internal control system is a strong signal by management that internal control is important. ... For an internal audit function to be effective, it is essential that the internal audit staff be independent from management, work in an unbiased, correct and honest way and that they report directly to the highest level of authority within the organisation. ... "For professional guidance, internal auditors should use the Professional Practices Framework (PPF) of the Institute of Internal Auditors (IIA) (...) Additionally, internal auditors should follow the INTOSAI Code of Ethics".

• AFROSAI: African Organization of Supreme Audit Institutions
• ARABOSAI: Arab Organization of Supreme Audit Institutions
• ASOSAI: Asian Organization of Supreme Audit Institutions
• CAROSAI: Caribbean Organization of Supreme Audit Institutions
• EUROSAI: European Organization of Supreme Audit Institutions. For more information please see website.
• OLACEFS: Organization of Latin American and Caribbean Supreme Audit Institutions. For more information please see website
• PASAI: Pacific Association of Supreme Audit Institutions

The following supreme audit institution are members of INTOSAI:^[9]

• Government performance auditing
• CGAP: Institute of Internal Auditors#Other certificates offered by the IIA
• INTOSAI Development Initiative
• Negative assurance and Positive assurance
• UNMAI