The Arab Socialist Union (Arabic: الاتحاد الاشتراكى العربى, al-Ittiḥād al-Ištirākī 'l-ʿArabī; French: L'Union Socialiste Arabe) is one of a number of loosely related political parties based on the principles of Nasserist Arab socialism in a number of countries.
The Arab Socialist Union was founded in Egypt in December 1962 by Gamal Abdel Nasser as the country's sole political party. The ASU grew out of his Free Officers Movement. The party's formation was just one part in Nasser's National Charter. The Charter set out an agenda of nationalisation, agrarian reform and constitutional reform, which formed the basis of ASU policy. The programme of nationalisation under Nasser saw seven billion Egyptian pounds of private assets transferred into the public sector. Banks, insurance companies, many large shipping companies, major heavy industries and major basic industries were converted to public control. Land reforms saw the maximum area of private land ownership successively reduced from 200 to 100 feddans. A 90% top rate of income tax was levied on income over ten thousand Egyptian pounds. Boards of directors were required to have a minimum number of workers, and workers and peasants were guaranteed at least half of the seats in the People's Assembly. The Charter also saw a shift in emphasis away from Egyptian nationalism towards Arab unity.
After Nasser's death in 1970, Anwar Sadat quickly moved away from his radical socialist position. The first seat change occurred in 1974, with Sadat's Infitah, or Open Door, economic policy, which allowed the emergence of a modern entrepreneurial and consumerist society. Then, in 1976, the beginning of political pluralism allowed three political platforms — left, centre and right — to form within the Arab Socialist Union. In 1978, the platforms were allowed to become fully independent political parties, and the ASU was disbanded. Many of today's political parties in Egypt have their origin in the breakup of the ASU.
The Arab Socialist Union goals at that point reflected the following:
- There should be state control over the national economy and the public sector should establish institutions to undertake the development process.
- Pan-Arab nationalism should be pursued.
- Class struggle is not required for arab socialism.
- The country should be answerable to the people and run as a democracy.
- Commitment to religion and freedom of faith and worship are essential.
Following the 1967 War and massive demonstrations in February and October 1969, Egypt was in a state of political turmoil, leading to raising calls for granting citizens more democratic rights and demanding self-expression for political affiliations.
Following assuming office in 1970, late president Anwar Sadat adopted the slogans of rule of law and the institutional state.
In August 1974, Sadat put forward a working paper to revamp the Arab Socialist Union.
In July 1975, the Arab Socialist Union's general conference adopted a resolution on establishing political forums within the union for expression of opinion in accordance with basic principles of the Egyptian Revolution.
In March 1976, president Sadat issued a decree allowing three forums to represent the right wing (the Liberal Socialist Organization), the center wing (Egypt Arab Socialist Organization) and the left wing (the National Progressive Unionist Organization).
These forums were later transformed into parties, forming today's Egyptian major political parties.
During the first meeting of the People's Assembly on November 22, 1976, president Sadat declared the three political organizations turned into parties. In June 1977, the law of political party was enacted, allowed the existence of several political parties and demonstrated the shift to a multi-party system. However the ratification of this law had not meant cancellation of the Arab Socialist Union, rather it had given the Union more powers to allow party formation.
The ASU in Syria grew out of an Egyptian-backed merger of several Nasserist opposition groups, all of them working illegally under Baath Party rule in the early 1960s. In 1972, the party gained legal recognition as a member of the National Progressive Front (NPF), a governing coalition that grouped all legal parties under Baathist supervision. The following year, the adoption of a constitution sidelining non-Baathist members of the coalition provoked a split, with the majority of the party deciding to leave the NPF. This group formed the Democratic Arab Socialist Union (DASU) to act in opposition under party leader Jamal al-Atassi, while a small rump faction under Fawzi Kiyali stayed on in the NPF, retaining the original name and legal status with Baathist government backing.
Since the death of al-Atassi, the DASU has been led by Hassan Abdelazim. It remains an illegal party and has been subject to sporadic repression; although it became semi-openly active after the accession of Bashar al-Assad to power in 2000, and under the limited liberalization that followed. The DASU is the leading member of the National Democratic Gathering, a nationalist-leftist opposition alliance founded in 1979.
The regime-backed ASU still exists as part of the NPF. It has very limited activity, but remains represented in Syrian politics largely thanks to NPF-controlled elections. It received 7 of the 250 seats in the Syrian legislature in 2003, and 8 in the 2007 elections.
Many aspects of Muammar al-Gaddafi's Libyan revolution were based on that of Gamal Abdel Nasser. Like Nasser, Qaddafi seized power with a Free Officers Movement, which, in 1971 became the Arab Socialist Union. Like its Egyptian counterpart, the Libyan ASU was the sole legal party, and was designed as a vehicle for integrated national expression rather than as a political party. In 1972, Qaddafi pushed hard for the formation of a Federation of Arab Republics, combining Libya with Egypt and Syria under his leadership, but the plan never took off. 1974 saw an attempt for union with Tunisia also fail.
In Iraq, the ASU after the overthrow of the Baathists in between time of Ramadan to the revolt of President Abd al-Salam Arif preferred and only officially authorized party, but could not effectively compete with the traditionally influential parties and power groups. The Iraqi Arab Socialist Union was founded in July 1964 came on the establishment of preparatory committee also not. These committees have failed in the goal to integrate the existing parties as well as on the task that was to promote planned by Nasser and Arif gradual economic, military and political union of Egypt and Iraq.  Chairman of the Iraqi ASU just the former secretary general of the Iraqi Baath Party, Fuad al-Rikabi. Iraqi ASU was the General Secretary and Information Minister Abdul Karim Farhan. Several smaller parties are dissolved and joined the IASU, the most important of these was a union with Nasser's Egypt oriented ANM. In September 1964 the Egyptian and Iraqi ASU were combined in a joint Executive Committee under Nasser's leadership. 
After the coup attempts by the Prime Minister Nasser Arif Abd ar-Razzaq (September 1965, July 1966) and Abdul Karim Farhan (October 1965) and the failure of the Egyptian-Iraqi union plans was put under the Iraqi ASU in October 1966 directly to the government. A group led by al-Rikabi split then as Arab Socialist Movement (ASM) from. Arif was instead in July 1968 was overthrown by a Baathist coup military, immediately dissolved the ASU Preparatory Committee and finally ar-Rikabi were thrown into prison (where he died in 1971). As in Syria, the Iraqi Baathists 1973-1979 rival progressive and patriotic parties tied in a coalition of the Progressive National Front, a patriotic, Nasserist was a movement it anymore.
- Rami Ginat (1997). Egypt's Incomplete Revolution: Lutfi Al-Khuli and Nasser's Socialism in the 1960s, Routledge.