Castilian War

Castilian War
	; Bruneian forces fighting Spanish forces
Date	16 April – 26 June 1578
Location	Borneo, Mindanao, and Sulu
Result	Status quo ante bellum
Belligerents
Bruneian Empire; Sulu Sultanate; Maguindanao	Spanish Empire Captaincy General of the Philippines; Bruneian defectors; ;
Commanders and leaders
Sultan Saiful Rijal; Bendahara Sakam; Muhammad ul-Halim; Datu Bangkaya	Francisco de Sande; Pengiran Seri Lela ; Pengiran Seri Ratna †
Units involved
Bruneian Army	Spanish Army 200 Spaniards; 200 Mexicans; 1,500 Filipinos; 300 Bruneians; ;
Strength
around ~1,000–5,000 warriors; 62 guns; 50 ships	2,200 men; 40 ships;
Casualties and losses
Unknown 170 artillery pieces; 27 ships and galleys captured	Unknown; presumably heavy; 17 men dead (by dysentery)

The Castilian War, also called the Spanish expedition to Borneo, was a conflict between the Spanish Empire and several Muslim states in Southeast Asia, including the Sultanates of Brunei, Sulu, and Maguindanao. It is also considered as part of the Ottoman-Habsburg Wars. This war is the beginning of relations between the Ottoman state and the Sultanate of Brunei in 1560 to 1578.