The flag of Syria (Arabic: علم سوريا) was re-adopted in 1980. The flag was formerly the flag of the United Arab Republic.
The first modern Syrian flag was adopted in 1920, and was similar to the current flag of Jordan with the green and white colours reversed. The colours and design were taken from the Pan-Arab flag and inspired by the flag of the Arab Revolt. The stars stand for the fact that Syria was the first country to use the Pan-Arab colors.
The French changed the flag of Syria under their mandate into a blue flag with a white crescent in the centre and a French flag in the canton. After a month the flag was changed into a horizontally striped green-white-green flag with a French tricolour in the canton. This Syrian flag was in use from 1925 until 1936 (along with flags of several cantons into which Syria was divided under French colonial rule). Then the flag of Syria was changed into a horizontally striped green-white-black tricolour flag with three red five-pointed stars in the centre of the white stripe. This followed the signing of the Franco-Syrian treaty which gave Syria partial independence. The first national flag of Syria after independence in 1946 was this green-white-black flag with three red stars.
In 1958, Syria and Egypt merged to form the United Arab Republic, the flag of which was derived from the Arab Liberation Flag of the Egyptian Revolution of 1952 (a tricolour of horizontal red, white, and black bands). The flag of the union was distinguished from the original Arab Liberation Flag by two green stars in the white band, symbolizing the two component parts of the union. As of 1980, this is once again the flag of Syria.
When Syria withdrew from the union in 1961, Egypt maintained both the name and flag of the United Arab Republic, whereas Syria reverted briefly to its old green-white-black flag. However, the Ba’athist coup in 1963 led to the re-introduction of the Arab Liberation Flag, this time with three green stars in the white band, symbolising the hoped for union of Syria, Egypt, and Iraq. Iraq also adopted this flag at the same time, and maintained it (with certain modifications) until 2008. Wikipedia