阿拉伯人進攻敘利亞始於629年，時伊斯蘭教先知穆罕默德尚在。宰德·伊本·哈列賽（穆罕默德的義子）率三千人於摩耳臺（死海南端的東面）襲擊東羅馬軍隊，戰敗，宰德陣亡。這也是穆斯林對基督教地區的第一次戰爭。
632年，穆罕默德去世。6月8日，艾卜·伯剋爾繼任，號哈裏發。633年秋，遣三支軍隊，以阿慕爾為總司令，攻敘利亞。634年，敗巴勒斯坦的羅馬貴族塞基阿斯。2月4日，殲滅羅馬潰兵於達辛。此後哈裏發艾卜·伯剋爾令哈立德·伊本·韋立德增援。3月，哈立德從伊拉剋邊境剛徵服的希拉城出發，急行軍十八天，至大馬士革。其中五天行於沙漠，以皮袋貯軍隊飲水，沿途宰駝供膳，以駝胃之水飲馬。軍士五百至八百人，乘駝，而備戰之馬空騎與駝並馳。會師後哈立德任聯軍最高指揮。7月30日，敗羅馬於艾衹那代。635年9月，圍攻大馬士革六個月後，降之。大馬士革投降的條約也成為以後各城投降阿拉伯人的範本，規定：阿拉伯統帥進城後答應保護居民的生命、財産和教堂，城墻不被拆除，任何穆斯林不駐紮在他們的房屋裏；居民需要繳納人丁稅：每人每年交一個第納爾和一袋小麥（在第二位哈裏發歐麥爾時代有所增加）。其後敘利亞諸城相繼陷落。
此時，東羅馬皇帝希拉剋略集結了五萬多人，以其弟西奧多拉斯為帥，抵禦阿拉伯人。哈立德暫棄霍姆斯、大馬士革諸城，於約旦河左岸雅穆剋河𠔌集二萬五千餘人與羅馬軍隊作戰。636年8月20日，天大熱，大敗東羅馬軍隊，殺西奧多拉斯。希拉剋略逃回。敘利亞遂歸屬阿拉伯。
639年，阿慕爾開始進軍埃及。640年7月，在阿因·捨木斯城擊潰東羅馬軍隊。642年9月，埃及首府亞歷山大港降，東羅馬軍隊撤退。而阿慕爾在巴比倫堡外的營地建成新都弗斯塔德（開羅）。埃及成為阿拉伯帝國的重要財政來源。
645年底，亞歷山大港人乞兵於東羅馬，君士坦斯皇帝派遣船三百艘收復亞歷山大港。而剛去職的阿慕爾得到復職，在尼丘擊敗東羅馬軍隊，646年初，重新占領亞歷山大港。649年，敘利亞長官穆阿威葉奪取塞浦路斯島。
In 639 an army of some 4,000 men was sent against Egypt by the second caliph, Umar, under the command of Amr ibn al-As. This army was joined by another 5,000 men in 640 and defeated a Byzantine army at the battle of Heliopolis. Amr next proceeded in the direction of Alexandria, which was surrendered to him by a treaty signed on November 8, 641.
Alexandria was regained for the Byzantine Empire in 645 but was retaken by Amr in 646. In 654 an invasion fleet sent by Constans II was repulsed. From that time no serious effort was made by the Byzantines to regain possession of the country.
In return for a tribute of money and food for the troops of occupation, the Christian inhabitants of Egypt were excused military service and left free in the observance of their religion and the administration of their affairs.
Conversions of Copts to Islam were at first rare, and the old system of taxation was maintained for the greater part of the first Islamic century. The old division of the country into districts (nomoi) was maintained, and to the inhabitants of these districts demands were directly addressed by the governor of Egypt, while the head of the community—ordinarily a Copt but in some cases a Muslim Egyptian—was responsible for compliance with the demand.
The resentment of the Copts against taxation, however, led to a revolt in 725. In 727, to strengthen Arab representation, a colony of 3,000 Arabs was set up near Bilbeis. Meanwhile, the employment of the Arabic language had been steadily gaining ground, and in 706 it was made the official language of the government. Egyptian Arabic, the modern language of Egypt, began to form. Other revolts of the Copts are recorded for the years 739 and 750, the last year of Umayyad domination. The outbreaks in all cases are attributed to increased taxation.
The Abbasid period was marked by new taxations, and the Copts revolted again in the fourth year of Abbasid rule. At the beginning of the 9th century the practice of ruling Egypt through a governor was resumed under Abdallah bin Tahir, who decided to reside at Baghdad, sending a deputy to Egypt to govern for him. In 828 another Egyptian revolt broke out. And in 831 the Copts joined with native Muslims against the government.
In the 9th century Egypt was mostly governed by Turks (Tulunids, Ikhshidids) ruling in the name of the Muslim governor. Egypt came into conflict with Syria and the Caliphate until peace was made in 891. In 914 Egypt was invaded for the first time by a Fatimid force sent by the Caliph al-Mahdi Obaidallah, now established at Kairawan. The Mahdi's son succeeded in taking Alexandria in 919, and Egypt wasn't freed from the invaders until the year 921, when reinforcements had been repeatedly sent from Baghdad to deal with them. In 969 the Fatimid general Jawhar as-Siqilli was placed at the head of an army said to number 100,000 men and attempted to seize Egypt. He had little difficulty defeating the Egyptian army. And on July 6, 969, he entered Fostat at the head of his forces. Egypt was transferred from the Eastern to the Western caliphate.