Cagayan de Oro; ( /kəˈɡaɪən deɪ ˈɔəroʊ/ kə-GY-ən day OHR-oh; Cebuano: Dakbayan sa Cagayan de Oro; Filipino: Lungsod ng Cagayan de Oro), officially the City of Cagayan de Oro, is the provincial capital city of the province of Misamis Oriental in the Philippines. It lies along the northern coastline of the island of Mindanao in the country's southern portion.

It is the regional center of Northern Mindanao, and the metropolitan center of Metro Cagayan de Oro. According to the 2010 Census, the city has an estimated population of 602,088 inhabitants.

Cagayan de Oro is known as the "City of Golden Friendship" (Dakbayan sa Bulawanong Panaghigala-ay in Cebuano, as the phrase appears on the city's seal). The name Cagayan de Oro may appear abbreviated as CDO, CDOC, CdeO or Cag. de Oro.

There are also other places in the Philippines with a Cagayán name. One must distinguish Cagayan de Oro from Cagayan province in Northern Luzon and the Cagayan Islands in the Sulu Sea.

The name Cagayán de Oro can be traced back during the arrival of the Spanish Augustinian Recollect friars in 1622, the area around Himologan (now Huluga), was already known as "Cagayan".

Cagayan (/kɑːɡəˈjɑːn/kah-gə-YAHN), the "Land of Smiling Beauty", is a province of the Philippines in the Cagayan Valley region in Luzon. Its capital is Tuguegarao City and is located at the northeastern corner of the island of Luzon. Cagayan also includes the Babuyan Islands to the north. The province borders Ilocos Norte and Apayao to the west, and Kalinga and Isabela to the south. Cagayan province is distinct from the city in Mindanao named Cagayan de Oro, and is far away from Cagayancillo of Palawan or Cagayan de Tawi-Tawi Island in the Sulu Sea.

Present day chroniclers say that the name was derived from the word “tagay,” a kind of plant that grows abundantly in the northern part of the province. Thus, “Catagayan” which means a place where the tagay grows abundantly was shortened to “Cagayan,” the present name of the province.

In 1581, Captain Juan Pablo Carreon came to Cagayan with one hundred fully equipped soldiers with their families by order of Gonzalo Ronquillo de Peñaloza, the fourth Spanish Governor-General of the Philippines, to explore the Cagayan Valley and to force the conversion of the natives to Catholicism as well as to establish ecclesiastical missions and towns throughout the valley. This was the first batch of Spanish settlers in the Cagayan Valley who introduced Spanish culture and Latin civilization, subverting native culture, customs, and tradition.