The Interparliamentary Assembly on Orthodoxy (Greek: Διακοινοβουλευτική Συνέλευση Ορθοδοξίας, Russian: Межпарламентская Ассамблея Православия), or I.A.O., is a transnational, inter-parliamentary institution that in 1994 was originally established as the European Interparliamentary Assembly on Orthodoxy (EIAO).

Based in Athens, Greece, the Interparliamentary Assembly on Orthodoxy constitutes a permanent communication structure between parliamentarians of member states aiming at unity in diversity of Orthodox Christians on the principles and values of Christianity and democracy.^[1]

Inspired by a conference held from 30 June to 4 July 1993 in Chalkidiki on the topic of "Orthodoxy in the New European Reality", the European Interparliamentary Assembly on Orthodoxy was formed by the initiative of the Hellenic Parliament.^[2] Following the 1993 Manifesto of the Participants, the official Founding Act was passed by the participants of the Founding Synod held in November 1994 in Athens.^[3] In 2001, groups of parliamentarians from Australia, Asia, Africa and the United States participated in the General Assembly, the organization was then renamed Interparliamentary Assembly on Orthodoxy (I.A.O.).^[2]

During the June 2004 General Assembly in Kyiv, Ukraine, it was decided to seek cooperation with the Parliamentary Union of the Organisation of Islamic Cooperation (P.U.I.C.). A co-operation agreement was drafted at a meeting of the two organizations on 22 March 2005, in Athens.^[2] On 19 May 2010, a cooperation agreement with the Pan-African Parliament was signed by PUIC's President Idriss Ndele Moussa and I.A.O.'s Secretary-General Anastasios Nerantzis^[4]

Massive protests broke out during the 2019 General Assembly in Tbilisi, Georgia, after the chairman of the assembly, a Russian communist named Sergei Gavrilov, made a number of public statements that were viewed by the Georgian public as denigrating Georgian sovereignty.^[5][6]

The delegation from Russia, as well as the delegations from Belarus and Syria, were unable to attend the 2023 General Assembly due to EU sanctions. The election of a Polish president ended the three decade long Russian control of the presidency.^[7]

The Assembly currently consists of parliamentary committees of 21 countries, mostly from Eastern Europe, including:^[8]

Additionally, delegations from Africa, Asia, Australia, the European Union, and the United States have been participating in the Assembly.

The I.A.O. has signed several cooperation agreements with various international organizations, including:^[10]

• Parliamentary Union of the Organisation of Islamic Cooperation, since March 2005
• Parliamentary Assembly of the Union State, since November 2011
• Pan-African Parliament, since May 2011
• Interparliamentary Assembly of the Eurasian Economic Union, since November 2011
• Parliamentary Assembly of the Black Sea Economic Cooperation (PABSEC), observer status mutually granted
• Inter-Parliamentary Union, observer status mutually granted
• Parliamentary Assembly of the Mediterranean, Memorandum of Understanding since February 2019

The I.A.O has also participated in United Nations General Assembly conferences, has signed cooperation treaties with the parliaments of Egypt, Iran and Lebanon, as well as explored future cooperation with the Baltic Assembly, the European Parliament and the International Catholic Legislators Network: ICLN.^[10]

• Christianity in Europe
• Politics of Europe
• Religion in Europe