The Free Syrian Army (Arabic: الجيش السوري الحر‎, al-Jaysh as-Sūrī al-Ḥurr, FSA) is a group of defected Syrian Armed Forces officers and soldiers, founded during the Syrian Civil War on 29 July 2011 by seven or eight defected Syrian officers. The group defined "all [Syrian] security forces attacking civilians" as their enemies, and said its goal was "to bring down the system" or "to bring this regime down". By January 2016, the FSA consists of "about 27 larger factions, each comprised of an average of 1,000 fighters as well as some smaller units or localized militias", with there being "thousands" of the latter kinds of brigades of various sizes.

On 23 September 2011, the Free Syrian Army merged with the Free Officers Movement (Arabic: حركة الضباط الأحرار‎, Ḥarakat aḑ-Ḑubbāṭ al-Aḥrār); Western observers like The Wall Street Journal considered the FSA since then the main military defectors group. 90% of the FSA consists of Sunni Muslims, but a small minority are (Shia) Alawites and some Druze fought in FSA units. Some FSA units are led by Druze. As for further ethnic minorities, a Palestinian rebel commander in the Yarmouk enclave in southern Damascus in 2012 considered his rebel brigade to be part of FSA.

The Syrian Army, officially the Syrian Arab Army (SAA) (Arabic: الجيش العربي السوري‎ al-Jaysh al-’Arabī as-Sūrī), is the land force branch of the Syrian Armed Forces. It is the dominant military service of the four uniformed services, controlling the most senior posts in the armed forces, and has the greatest manpower, approximately 80 percent of the combined services. The Syrian Army originated in local military forces formed by the French after World War I, after France obtained a mandate over the region. It officially came into being in 1945, before Syria obtained full independence the following year.

Since 1946, it has played a major role in Syria's governance, mounting five military coups (two in 1949, including the March 1949 Syrian coup d'état and the August 1949 coup by Colonel Sami al-Hinnawi, 1954, 1963, 1966, and in 1970. It has fought four wars with Israel (1948, the Six Day War in 1967, 1973, and 1982 in Lebanon) and one with Jordan (Black September in Jordan, 1970). An armored division was also deployed to Saudi Arabia in 1990–91 during the Persian Gulf War, but saw little action. From 1976 to 2005 it was the major pillar of the Syrian occupation of Lebanon. Internally, it played a major part in suppressing the 1979–82 Islamist uprising in Syria, and since early 2011 has been heavily engaged in fighting the Syrian Civil War, the most violent and prolonged war the Syrian Army has taken part in since its establishment in the 1940s.