Sayyid Muhammad Rashīd Rida Al-Hussaini (Arabic: سيد محمد رشيد رضا الحسيني, romanized: Muḥammad Rashīd Riḍā; 1865 – 22 August 1935) was an Islamic scholar, reformer, theologian and revivalist. An early Salafist, Rida called for the revival of hadith studies and, as a theoretician of an Islamic state, condemned the rising currents of secularism and nationalism across the Islamic world following the abolition of the Ottoman sultanate. He championed a global pan-Islamist program aimed at re-establishing a Caliphate to unite diverse peoples under a single global Islamic authority.

As a young hadith student who studied al-Ghazali and Ibn Taymiyya, Rida believed reform was necessary to save the Muslim communities, eliminate Sufist practices he considered heretical, and initiate an Islamic renewal. He left Syria to work with Abduh in Cairo, where he was influenced by Abduh's Islamic Modernist movement and began publishing al-Manar in 1898. Through al-Manar's popularity across the Islamic world, Rida became one of the most influential Sunni jurists of his generation, leading the Arab Salafi movement and championing its cause.

He was Abduh's de facto successor and was responsible for a split in Abduh's disciples into one group rooted in Islamic modernism and the other in the revival of Islam. Salafism, also known as Salafiyya, which sought the "Islamization of modernity," emerged from the latter.

During the 1900s Rida abandoned his initial rationalist leanings and began espousing Salafi-oriented methodologies such as that of the Ahl-i Hadith movement. He later supported the Wahhabi movement, revived works by Ibn Taymiyyah, and shifted the Salafism movement into a more conservative and strict Scripturalist approach. He is regarded by a number of historians as "pivotal in leading Salafism's retreat" from the rationalist school of Abduh. He strongly opposed liberalism, Western ideas, freemasonry, Zionism, and European imperialism, and supported armed Jihad to expel European influences from the Islamic World. He also laid the foundations for anti-Western, pan-Islamist struggle during the early 20th century.

Muhammad Rashid Rida was born in al-Qalamoun, Beirut Vilayet, present-day Lebanon, in 1865 into a distinguished Sunni Shafi'i clerical family. His family relied on money earned from their limited olive tree holdings and fees earned by family members who served as ulama (scholars). The Rida ulama had been in charge of the al-Qalamoun mosque for several generations. Rida's father was an imam (prayer leader) in the mosque. The family, who were Sayyids, claimed descent from the Ahl al-Bayt, specifically Husayn ibn Ali.

Rida received a traditional religious education, attending elementary school at the local kuttab in Qalamūn before moving to the Ottoman government school in Tripoli. He then enrolled in Shaykh Ḥusayn al-Jisr [fr]'s National Islamic School, where he learned hadith and fiqh. He also earned a diploma of ulema in 1897. During his education, he studied the books and treatises of scholars such as Ibn Taymiyyah, Ibn Qayyim, Ibn Qudama, al-Ghazali, al-Mawardi, Razi, Taftasani, and Ibn Rajab. Rida began preaching at the communal level and taught tafsir and other religious sciences at the village's central mosque. He also taught separate ibadah classes for women. Around this time, he first read al-Urwa al-Wuthqa, a periodical that was highly influential to him. It was published by Jamal al-Din al-Afghani and Muhammad Abduh. According to Lebanese-British historian Albert Hourani, Rida belonged to the last generation of traditionally trained Islamic scholars who could be "fully educated and yet alive in a self-sufficient Islamic world of thought."

Rida met Muhammad Abduh, one of the editors of Al-Urwah al-Wuthqa, as an exile in Lebanon in the mid-1880s and quickly came to view Abduh as his mentor. In 1897, Rida decided to study under Abduh's co-editor Jamal al-Din al-Afghani, who at that time was in Istanbul. Rida suspected the Hamidian administration was responsible for al-Afghani's death later that year and left Istanbul to rejoin Abduh, one of Afghani's students, now in Egypt. They started the monthly periodical al-Manar, where Rida worked as its chief editor and owner until his death in 1935. At this time, he also studied Ibn Taymiyya and his disciples, which eventually led him to embrace ideas including revulsion against folk Sufism, criticism of taqlid, and the desire to revive hadith studies. All of these became foundational themes of the Salafism.

Following Abduh's death in 1905, Rida was seen as his de facto successor despite privately holding reservations about Abduh's ideas. Rida published several new editions of Abduh's works to make them conform more to the dogmas of the traditionalist creed than to Abduh's modernist beliefs. When interest in Abduh was revived in Egypt around the 1930s, the difference in narrative became more apparent. While Abduh's other disciples, Uthman Amin, Mustafa 'Abd al-Raziq, and Muhammad Naji, painted him as a rationalist, Rida continued to ascribe his own beliefs to Abduh's legacy, either ignoring or outright removing Abduh's more liberal ideas from the new editions of his works. Eventually, Rida's narrative became the dominant perception. Abduh's disciples eventually divided into two camps: one, which included Saad Zaghloul and Ali Abdel Raziq, was founded in modernism and Westernized secularism, and the other, the al-Manar party, was based in the revival of Islam. Salafism, also known as Salafiyya, which sought the "Islamization of modernity," emerged from the latter.