Muslim conquests (, al-Ġazawāt or الفتوحات الإسلامية, al-Fatūḥāt al-Islāmiyya) also referred to as the Islamic conquests or Arab conquests,Martin Sicker (2000), The Islamic World in Ascendancy: From the Arab Conquests to the Siege of Vienna, 'Praeger. began after the death of the Islamic prophetMuhammad. He established a new unified polity in the Arabian Peninsula which under the subsequent Rashidun (The Rightly Guided Caliphs) and UmayyadCaliphates saw a century of rapid expansion of Muslim power.
The Muslim conquests brought about the collapse of the Sassanid Empire and a great territorial loss for the Byzantine Empire. The reasons for the Muslim success are hard to reconstruct in hindsight, primarily because only fragmentary sources from the period have survived. Most historians agree that the Sassanid Persian and Byzantine Roman empires were militarily and economically exhausted from decades of fighting one another.