The Council of Indonesian Muslim Associations Party (Indonesian: Partai Majelis Syuro Muslimin Indonesia), better known as the Masyumi Party, was a major Islamic political party in Indonesia during the Liberal Democracy Era in Indonesia. It was banned in 1960 by President Sukarno for supporting the Revolutionary Government of the Republic of Indonesia (PRRI) rebellion.

In 1909, a trade organization called the Islamic Trading Association (Indonesian: Sarekat Dagang Islam) was established in Java, then part of the Dutch East Indies, to protect the interests of batik traders in the face of competition from ethnic Chinese merchants. In 1912, this became the Sarekat Islam (Islamic Union) and was headed by Western-educated Oemar Said Tjokroaminoto.

Although it began as a non-political organization, it began to speak out against injustice and poverty. By 1918, it had 450,000 members. Communist influence within it grew, but so did that of the reformist Islamic Muhammadiyah organization, which was anti-communist. In 1920, Muhammadiyah merged into Sarkat Islam. In 1923, Tjokroaminoto moved to expel communists from the organization at the SI Congress and established the Islamic Union Party (Indonesian: Partai Sarekat Islam - PSI), which adopted a policy of non-collaboration with the Dutch.

In 1929 the party was renamed the Indonesian Islamic Union Party (PSII). The next few years saw splits within the party, worsened by the death of Tjokroaminoto in 1937. In September 1937, Muhammadiyah and the traditionalist Nahdlatul Ulama established the Supreme Islamic Council of Indonesia (MIAI), an umbrella group for Islamic organizations. Following their 1942 invasion of the Dutch East Indies, the Japanese authorities banned the PSII but allowed the MIAI to continue. However, it became dominated by former PSII members, so it in turn was dissolved in 1943.

In November the Japanese established an organization called the Council of Indonesian Muslim Associations (Masyumi) in an attempt to control Islam in Indonesia. It too included Muhammadiyah and the Nahdlatul Ulama. However, Muslims resented the attempt to use them as tools of the Japanese and were especially angered by the obligation to bow towards the Imperial Palace in Tokyo (kyūjō-yōhai [ja]), rather than Mecca. However, the new organization became highly politicized and established a network across the country.

Following the Indonesian Declaration of Independence, on 7 November 1945 a new organization called Masyumi was formed. The founders wanted to take advantage of the organization's fame and structure, but there was considerable discussion as to whether to retain the name, due to its association with the Japanese occupiers. Its membership included key figures from the wartime Masyumi such as Hasyim Asy'ari and Wahid Hasyim, the PSII, and non-political Islamic organizations such as the traditionalist Nahdlatul Ulama and the modernist Muhammadiyah. The main leaders were Mohammad Natsir, Mohammad Roem, Sjafruddin Prawiranegara, Jusuf Wibisono and Abu Hanafi.

Its chief aims were the achievement of Indonesian independence and the establishment of a state governed by Islamic principles. It was strongly anti-communist. Along with the Indonesian National Party (PNI) and the Socialist Party of Indonesia (PSI), it played a dominant role in Indonesian politics from 1945 to 1949. Two Masyumi members, including Natsir, served in the cabinet appointed in November 1945, while 35 Masyumi members were appointed to the Central Indonesian National Committee, and four to its Working Committee. Masyumi members subsequently served in the first and second Hatta cabinets and in the cabinet of the short-lived United States of Indonesia. In April 1947, the PSII left Masyumi following disagreements with the leadership, particularly Natsir.

There were two main factions within the party. The first, led by Natsir, attracted support from the younger generation who had participated in the Indonesian National Revolution and from the non-Javanese membership. The second faction, headed by Soekiman Wirjosandjojo, was supported by ethnic Javanese members, and had closer links with the Nahdlatul Ulama, the PNI leadership, and President Sukarno. The party as a whole had more support from non-urban areas of Indonesia. It also controlled its newspaper, Abadi.