Arabic: , romanized: Qalat al-in, also called Hisn al-Akrad (Arabic: , romanized: in al-Akrd, lit.'Fortress of the Kurds') and formerly Crac de l'Ospital; Krak des Chevaliers or Crac des Chevaliers (French pronunciation: [kak de ()valje]), is a medieval castle in Syria and one of the most important preserved medieval castles in the world. The site was first inhabited in the 11th century by Kurdish troops garrisoned there by the Mirdasids. In 1142 it was given by Raymond II, Count of Tripoli, to the order of the Knights Hospitaller. It remained in their possession until it fell in 1271.

The Hospitallers began rebuilding the castle in the 1140s and were finished by 1170 when an earthquake damaged the castle. The order controlled a number of castles along the border of the County of Tripoli, a state founded after the First Crusade. Krak des Chevaliers was among the most important, and acted as a center of administration as well as a military base. After a second phase of building was undertaken in the 13th century, Krak des Chevaliers became a concentric castle. This phase created the outer wall and gave the castle its current appearance. The first half of the century has been described as Krak des Chevaliers' "golden age". At its peak, Krak des Chevaliers housed a garrison of around 2,000. Such a large garrison allowed the Hospitallers to exact tribute from a wide area. From the 1250s the fortunes of the Knights Hospitaller took a turn for the worse and in 1271 Mamluk Sultan Baibars captured Krak des Chevaliers after a siege lasting 36 days, supposedly by way of a forged letter purportedly from the Hospitallers' Grand Master that caused the Knights to surrender.

Renewed interest in Crusader castles in the 19th century led to the investigation of Krak des Chevaliers, and architectural plans were drawn up. In the late 19th or early 20th century a settlement had been created within the castle, causing damage to its fabric. The 500 inhabitants were moved in 1933 and the castle was given over to the French Alawite State, which carried out a program of clearing and restoration. When Syria declared independence in 1946, it assumed control.

Today, a village called al-Husn exists around the castle and has a population of nearly 9,000. Krak des Chevaliers is approximately 40 kilometres (25 mi) west of the city of Homs, close to the border of Lebanon, and is administratively part of the Homs Governorate. Since 2006, the castles of Krak des Chevaliers and Qal'at Salah El-Din have been recognised by UNESCO as World Heritage Sites. It was partially damaged in the Syrian civil war from shelling and recaptured by the Syrian government forces in 2014. Since then, reconstruction and conservation work on the site had begun. Reports by UNESCO and the Syrian government on the state of the site are produced yearly.

Syria (Arabic: سُورِيَا or سُورِيَة, Sūriyā), officially the Syrian Arab Republic (Arabic: ٱلْجُمْهُورِيَّةُ ٱلْعَرَبِيَّةُ ٱلسُّورِيَّةُ, romanized: al-Jumhūrīyah al-ʻArabīyah as-Sūrīyah), is a country in Western Asia. Syria borders the Mediterranean Sea to the west, Turkey to the north, Iraq to the east and southeast, Jordan to the south, and Israel and Lebanon to the southwest. Cyprus lies to the west across the Mediterranean Sea. A country of fertile plains, high mountains, and deserts, Syria is home to diverse ethnic and religious groups, including the majority Syrian Arabs, Kurds, Turkmens, Assyrians, Armenians, Circassians, Mandaeans, and Greeks. Religious groups include Sunnis, Christians, Alawites, Druze, Isma'ilis, Mandaeans, Shiites, Salafis, and Yazidis. The capital and largest city of Syria is Damascus. Arabs are the largest ethnic group, and Sunnis are the largest religious group.

Syria is a unitary republic consisting of 14 governorates and is the only country that politically espouses Ba'athism. It is a member of one international organization other than the United Nations, the Non-Aligned Movement; it was suspended from the Arab League in November 2011 and the Organisation of Islamic Cooperation, and self-suspended from the Union for the Mediterranean.The name "Syria" historically referred to a wider region, broadly synonymous with the Levant, and known in Arabic as al-Sham. The modern state encompasses the sites of several ancient kingdoms and empires, including the Eblan civilization of the 3rd millennium BC. Aleppo and the capital city Damascus are among the oldest continuously inhabited cities in the world. In the Islamic era, Damascus was the seat of the Umayyad Caliphate and a provincial capital of the Mamluk Sultanate in Egypt.

The modern Syrian state was established in the mid-20th century after centuries of Ottoman rule, and after a brief period as a French mandate, the newly created state represented the largest Arab state to emerge from the formerly Ottoman-ruled Syrian provinces. It gained de jure independence as a parliamentary republic on 24 October 1945, when the Republic of Syria became a founding member of the United Nations, an act which legally ended the former French Mandate, although French troops did not leave the country until April 1946.

The post-independence period was tumultuous, with many military coups and coup attempts shaking the country from 1949 to 1971. In 1958, Syria entered a brief union with Egypt called the United Arab Republic, which was terminated by the 1961 Syrian coup d'état. The republic was renamed as the Arab Republic of Syria in late 1961 after the December 1 constitutional referendum of that year, and was increasingly unstable until the 1963 Ba'athist coup d'état, since which the Ba'ath Party has maintained its power. Syria was under Emergency Law from 1963 to 2011, effectively suspending most constitutional protections for citizens.

Bashar al-Assad has been president since 2000 and was preceded by his father Hafez al-Assad, who was in office from 1971 to 2000. Throughout his rule, Syria and the ruling Ba'ath Party have been condemned and criticized for various human rights abuses, including frequent executions of citizens and political prisoners, and massive censorship. Since March 2011, Syria has been embroiled in a multi-sided civil war, with a number of countries in the region and beyond involved militarily or otherwise. As a result, a number of self-proclaimed political entities have emerged on Syrian territory, including the Syrian opposition, Rojava, Tahrir al-Sham and the Islamic State group. Syria was ranked last on the Global Peace Index from 2016 to 2018, making it the most violent country in the world due to the war. The conflict has killed more than 570,000 people, caused 7.6 million internally displaced people (July 2015 UNHCR estimate) and over 5 million refugees (July 2017 registered by UNHCR), making population assessment difficult in recent years.