Jamaat-e-Islami is an Islamist movement founded in 1941 in British India by the Islamist author and theorist Syed Abul Ala Maududi, who was inspired by the Muslim Brotherhood. It is considered one of the most influential Islamist organisations, and was the first to develop an ideology based on the modern revolutionary conception of Islam. Its founding branch in Pakistan is the nation's largest fundamentalist party.

Jamaat-e-Islami was founded to spread Islamic values across the Indian subcontinent and advocate for an Islamic political system. It was formed on 26 August 1941 in Lahore under the leadership of Maududi, who believed that contemporary political ideologies resulted from Western imperialism, and that it was necessary to implement Sharia law to preserve Muslim culture. Maududi believed politics was "an integral, inseparable part of the Islamic faith," and that Islamic ideology and non-Islamic ideologies (such as capitalism and socialism, liberalism or secularism) were mutually exclusive. He saw the creation of an Islamic state as both act of piety, and a cure for social and economic problems faced by Muslims, which he attributed to Western influence.

Jamaat-e-Islami opposed the partition of India and the creation of Pakistan and actively worked to prevent it. After the partition of India, the organisation spearheaded the movement to transform Pakistan from a Muslim homeland into an Islamic state. Madudi's efforts focused on transforming to a "theo-democracy" based on the Sharia which would enforce things like abolition of interest-bearing banks, sexual separation, veiling of women, hudud penalties for theft, adultery, and other crimes. Jamaat seeks to spur an Islamic revival, implementing Islam as a universal religion.

Jamaat-e-Islami Kashmir movement is banned in the state of Jammu and Kashmir in India, while the movement in Bangladesh has faced bans historically, most recently in 2024, although the decision was later reversed by the interim government. Since 2003, the organisation is designated as a terrorist organisation by Russia for its close relations with the Muslim Brotherhood.

Maududi opposed British rule but also opposed both the anti-colonialist Muslim nationalist Muslim League's proposal for a separate Muslim state led by Muhammad Ali Jinnah, and the composite nationalism (muttahida qaumiyyat) idea of Jam'iyyat al-Ulama-ye Hind and Deobandi scholar Maulana Sayyid Hussain Ahmad Madani for a united independent India with separate institutional structures for Hindus and Muslims.

In 1940, the Muslim League met in Lahore and passed the Lahore Resolution, calling for autonomous states in the Muslim-majority areas of India. Maududi believed that Islam is a universal religion that calls for a single, globally unified government and therefore nationalism in any form was un-Islamic. In response he launched his own party, Jamaat-e-Islami, founded on 26 August 1941, at Islamia Park, Lahore. Seventy-five people attended the first meeting and became the first 75 members of the movement.

Maududi saw his group as a vanguard of Islamic revolution following the footsteps of early Muslims who gathered in Medina to found the first "Islamic state". Members uttered the Shahada, the traditional statement of conversion to Islam, when they joined, implying to some that Jama'ati felt they had been less-than-true Muslims before joining. Jamaat-e-Islami was and is strictly and hierarchically organised in a pyramid-like structure. All supporters work toward the common goal of establishing an ideological Islamic society, particularly through educational and social work, under the leadership of the emir. Being a vanguard party, not all supporters could be members, only the elite. Below members were/are "affiliates", and "sympathisers" beneath them. The party leader is called an ameer (commander).

Maududi sought to educate the elite of the Muslim community in the principles of Islam and correct "their erroneous ways of thinking" both because he believed societies were influenced from the top down.