The conquest of Oran by the Hispanic Monarchy took place on May 1509, when an army led by Pedro Navarro on behalf of the Cardinal Cisneros seized the north-African city, which was controlled by the moors of Tlemcen.
A fleet left port from Cartagena on 16 May and sailed towards Mers el-Kebir, a city located near Oran and already (since 1505) under Spanish control. The fleet had 80 naos and 10 galleys, plus additional small boats. They carried around 8000-12,000 infantry-men and 3000-4000 cavalry-men. The army spent the night of 17 May in Mers el Kebir.The Christians stormed the city of Oran, then part of the Kingdom of Tlemcen, combining the use of the fleet with a ground assault on 18 May. After breaking through the walls of the city the casualties numbered less than 30 on the assaulting side, while the 12,000 defenders suffered 4,000 casualties.
On 20 May, Cisneros entered the city, already conquered.
The city remained a part of the Spanish Empire until 1708, when it was seized by the Ottoman Dey of Algiers taking advantage of the War of the Spanish Succession. The city was conquered again by the Spanish in 1732. After the 1790 earthquake, they abandoned Oran and Mers el-Kebir in 1792.