Khawabi (Arabic: الخوابي), also spelled Qal'at al-Khawabi (Arabic: قلعة الخوابي) is a village and medieval citadel in northwestern Syria, administratively part of the Tartus Governorate, located 20 kilometers northeast of Tartus and 12 kilometers east of al-Sawda. According to the Syria Central Bureau of Statistics, Khawabi had a population of 1,039 in the 2004 census. Its inhabitants are predominantly Sunni Muslims. The village formerly had a significant Ismaili population until the early 20th century, and during the medieval period, its citadel (Qal'at Khawabi) served as a center of the Ismaili community when they were known as the Assassins. The citadel itself has been inhabited since at least the 12th century.

Khawabi is situated in a hilly area, surrounded by olive groves, in the Coastal Mountain Range. Nearby localities include al-Sawda and to the west, Al-Annazah to the northwest, al-Qamsiyah to the north, Brummanet Raad to the northeast, al-Shaykh Badr to the east, Khirbet al-Faras to the south and Bimalkah to the southwest.

Like many of the other castles in coastal Syria, the castle of Khawabi has its origins in the Phoenician era (1200–539 BC). In 985, under Muslim rule, the geographer al-Muqaddasi noted that Hisn al-Khawabi ('the Citadel of Khawabi') was part of Jund Hims (the military district of Homs). In 1025, when the area was controlled by the Byzantine Empire, the citadel was restored by the Byzantines. Khawabi later came into the possession of one Muhammad ibn Ali ibn Hamid.

The Crusaders, who referred to the citadel as La Coible, acquired Khawabi from its owner, Ibn Hamid, in 1111 and assigned its governorship to a local lord. However, author and expert in Isma'ili studies, Peter Willey, notes that there is no evidence the Crusaders ever held it, though they did refer to it as Coible and considered it an endangerment to their coastal mountain positions. A short time following the Nizari Isma'ilis' capture of Masyaf in 1141, they proceeded to conquer Khawabi. By the time the Isma'ili chief Rashid al-Din Sinan renovated the citadel into a formidable possession in 1160, Khawabi had developed into an Isma'ili religious center. Part of Sinan's renovations included the construction of a tower at the citadel's entrance and the replacement of some walls. Khawabi became geostrategically important for the Isma'ilis since it provided further defense for other Isma'ili mountain fortresses to its southwest.

After the Isma'ilis assassinated Raymond, the eldest son of Bohemond IV, prince of Antioch at the Cathedral of Our Lady of Tortosa in Tartus, Bohemond and a reinforcement of Templars assaulted Khawabi in 1214. The Isma'ilis requested aid from the Ayyubid ruler of Aleppo, az-Zahir Ghazi, who in turn appealed to his rival and uncle al-Adil, the Ayyubid sultan of Egypt. Az-Zahir's relief army was dealt a major setback when the Muslim force was nearly destroyed in a Crusader ambush at Jabal Bahra, on the approaches of Khawabi. However, after al-Adil's son, al-Mu'azzam of Damascus, launched several raids against Bohemond's district of Tripoli, destroying all of its villages, Bohemond was compelled to withdraw from Khawabi and issue an apology to az-Zahir.

The Isma'ilis maintained their control over Khawabi until the beginning of Mamluk rule in Syria. In 1273 the Mamluk sultan Baybars annexed and destroyed the citadel. From that point on, although the Ismailis had continued to live in the area with limited autonomy under Mamluk rule, the dismantled fortress was no longer used for military purposes. The remainder of the castle's infrastructure was adapted for agricultural or domestic purposes. In 1484 the Mamluk sultan Qaytbay ended the tax on loom products, cattle slaughtering and shoe repairing for Khawabi and nearby al-Kahf.

During the Ottoman period (1516–1918), the Khawabi citadel became a center of Khawabi Nahiya (Nahiye Havabi in Turkish; 'subdistrict of Khawabi'). The Khawabi Nahiya was originally part of the Tripoli Sanjak, part of the larger Tripoli Eyalet. In 1563 Khawabi was administrativelty separated to form part of the Jableh Sanjak, along with several other subdistricts in the coastal mountain range. The Sha'ir family from Tripoli served as the governors of Khawabi in the 18th century after being driven out of Batroun.

In 1831 the citadel and its nahiya became one of the 13 subdistricts of the Latakia Sanjak, then under the authority of the governors of Acre. In 1865 Khawabi was reassigned to the Marqab Sanjak, part of the larger province of Tripoli. The Ottomans constructed a mosque in 1892–93 named after Sultan Abdul Hamid II. The administrative region of Khawabi contained a mixture of religious sects according to the Ottoman census of 1878. Alawites constituted 47% of its total population of 1,837, Isma'ilis 19%, Greek Orthodox Christians 15%, Sunni Muslims 14% and Maronite Christians 5%. The Sunni inhabitants of Khawabi's fortress village descend from the mainly Kurdish tribesmen settled there by Baybars or his 13th-century successors. By the early 20th century, towards the ends of Ottoman rule, the Sunni notables and aghas of Khawabi owned vast tracts of land inhabited by Alawite farming communities between Duraykish and Qadmus and the fortress village served as the nahiye headquarters. The French novelist Maurice Barrès, who visited in 1914, noted that the agricultural products of the nahiye flowed to Khawabi's market.