Angelokastro (Greek: Αγγελόκαστρο (Castle of Angelos or Castle of the Angel); Venetian: Castel Sant'Angelo) is a Byzantine castle on the island of Corfu, Greece. It is located at the top of the highest peak of the island's shoreline in the northwest coast near Palaiokastritsa and built on particularly precipitous and rocky terrain. It stands 1,000 ft (305 m) on a steep cliff above the sea and surveys the City of Corfu and the mountains of mainland Greece to the southeast and a wide area of Corfu toward the northeast and northwest.

Angelokastro is one of the most important fortified complexes of Corfu. It was an acropolis which surveyed the region all the way to the southern Adriatic and presented a formidable strategic vantage point to the occupant of the castle. Angelokastro formed a defensive triangle with the castles of Gardiki and Kassiopi, which covered Corfu's defences to the south, northwest and northeast. The castle never fell, despite frequent sieges and attempts at conquering it through the centuries, and played a decisive role in defending the island against pirate incursions and during three sieges of Corfu by the Ottomans, significantly contributing to their defeat. During invasions, it helped shelter the local peasant population. The villagers also fought against the invaders playing an active role in the defence of the castle.

The exact period of the building of the castle is not known, but it has often been attributed to the reigns of Michael I Komnenos and his son Michael II Komnenos. The first documentary evidence for the fortress dates to 1272, when Giordano di San Felice took possession of it for Charles of Anjou, who had seized Corfu from Manfred, King of Sicily in 1267.

From 1387 to the end of the 16th century, Angelokastro was the official capital of Corfu and the seat of the Provveditore Generale del Levante, governor of the Ionian islands and commander of the Venetian fleet, which was stationed in Corfu. The governor of the castle (the castellan) was normally appointed by the City council of Corfu and was chosen amongst the noblemen of the island.

Angelokastro is considered one of the most imposing architectural remains in the Ionian Islands, along with Kassiopi Castle, Gardiki Castle and the two Venetian Fortresses of Corfu City, the Citadel and the New Fort.

The name may be related to the Komnenoi Angeloi, Despots of Epirus. The earliest textual reference to the castle is in an Angevin document of 1272, which refers to it as Castrum Sancti Angeli or Castrum S. Angeli, 'Castle of the Holy Angel'. Venetian documents of the 17th century call it Castel or Castello Sant' Angelo.

Angelokastro is one of the most important fortified complexes of Corfu. It forms an acropolis that surveyed the region all the way to the southern Adriatic and therefore presented a formidable strategic vantage point to the occupant of the castle. Situated at an impregnable and strategic position, Angelokastro became important to the island's fortunes for many centuries.

Angelokastro was one of three castles which defended the island before the Venetian era (1401–1797). The castles formed a defensive triangle, with Gardiki Castle guarding the island's south, Kassiopi Castle the northeast and Angelokastro the northwest.