Oaxaca de Juárez (Spanish pronunciation: [waˈxaka ðe ˈxwaɾes]), or simply Oaxaca (Valley Zapotec: Ndua), is the capital and largest city of the eponymous Mexican state of Oaxaca. It is the municipal seat for the surrounding municipality of Oaxaca, the most populous municipality in Oaxaca and the fourth most densely populated municipality in Oaxaca, only being less densely populated than San Jacinto Amilpas, Santa Lucía del Camino, and Santa Cruz Amilpas. It is in the Centro District in the Central Valleys region of the state, in the foothills of the Sierra Madre at the base of the Cerro del Fortín, extending to the banks of the Atoyac River.

Heritage tourism makes up an important part of the city's economy, and it has numerous colonial-era structures as well as significant archeological sites and elements of the continuing native Zapotec and Mixtec cultures. The city, together with the nearby archeological site of Monte Albán, was designated in 1987 as a UNESCO World Heritage Site. It is the site of the month-long cultural festival called the "Guelaguetza", which features Oaxacan dance from the seven regions, music, and a beauty pageant for indigenous women.

The city is also known as la Verde Antequera (the green Antequera) due to its prior Spanish name (Nueva Antequera) and the variety of structures built from a native green stone. The name Oaxaca is derived from the Nahuatl name for the place, Huaxyacac, which was Hispanicized to Guajaca, later spelled Oaxaca. In 1872, "de Juárez" was added in honor of Benito Juárez, a native of this state who became president, serving from 1852 to 1872, and leading the country through challenges, including an invasion by France. The Zapotec name of the city, Ndua, is still used in the Zapotec language (Tlacolula Zapotec). The coat of arms for the municipality bears the image of Donají, a Zapotec woman hostage killed and beheaded by the Mixtec in conflict immediately after the Conquest.

The Zapotec and Mixtec peoples had settlements in the valley of Oaxaca for thousands of years, especially in connection with the important ancient centers of Monte Albán and Mitla. The modern city of Oaxaca developed relatively near them. The Aztecs entered the valley in 1440 and named it "Huaxyacac", a Nahuatl phrase meaning "among the huaje" (Leucaena leucocephala) trees. They created a strategic military position at what is now called the Cerro (large hill) del Fortín to oversee the Zapotec capital of Zaachila and secure the trade route between the Valley of Mexico, Tehuantepec, and what is now Central America.

When the Spanish arrived in 1521, the Zapotec and the Mixtec were involved in one of their many wars. The Spanish conquest ended this fighting, imposing a kind of imperial peace on the area. At the same time, Spanish Catholic missionaries began evangelizing the indigenous peoples, urging them to conversion.

The first Spanish expedition to Oaxaca arrived late in 1521, headed by Captain Francisco de Orozco who was accompanied by 400 Aztec warriors. Hernán Cortés sent Francisco de Orozco to Oaxaca because Moctezuma II had said that the Aztecs' gold came from there. The Spanish expedition under Orozco set about building a Spanish city where the Aztec military post was at the base of the Cerro de Fortín.

The first mass in Oaxaca was given by Chaplain Juan Díaz on the bank of the Atoyac River under a large huaje tree, where the Church of San Juan de Dios would be constructed later. This same chaplain added saints' names to the surrounding villages, in addition to keeping their Nahuatl names: Santa María Oaxaca, San Martín Mexicapan, San Juan Chapultepec, Santo Tomas Xochimilco, San Matías Jalatlaco, Santiago Tepeaca, etc. This group of Spaniards chose their first mayor, Gutierres de Badajoc, and their first town council, and began construction of the cathedral of Oaxaca in 1522. Their name for the settlement was Guajaca, a Hispanization of the Nahuatl name used by the Aztec (it was later spelled as Oaxaca).

The relatively independent village did not suit Hernán Cortes, who wanted to control power over the entire region. Cortés sent Pedro de Alvarado, who proceeded to drive out most of the village's population. The original Spanish settlers appealed to the Spanish crown to recognize the village they founded, which it did in 1526, dividing the land among the Spaniards of Orozco's expedition. But three months later, Cortés forced out the population of the village once again and replaced the town council with his own appointees. The original founders appealed again to Spanish royal authority, this time to the viceroy in Mexico City, Nuño de Guzmán. He also sided with the original founders; they reestablished the town in 1529, naming it Antequera, in honor of Nuño de Guzmán's hometown. Francisco de Herrera convened the new, Crown-approved town council. Juan Peláez de Berrio platted the new settlement.