Sofia was settled in Neolithic times by the Thracian tribe called the Serdi. It was later held by the Macedonians and the Romans. The latter called it Serdica. Later the Slavs would conquer the area, absorbing the Thracian and Illyrian tribes. Their language took precedence over the native tongues. A warlike Turkish tribe, the Proto-Bulgars settled through the region, blending with the Slavic-Thracian mix. Sofia came into prominence towards the end of this First Bulgarian Empire (681-1018), but was conquered by the Byzantines who changed its name to Triaditza. The city was retaken in 1194, after establishment of the Second Bulgarian Empire in 1185. Sometime before the Ottoman conquest of the city in 1382, the city was renamed Sofia after St. Sofia, whose church had existed since ancient times.

Twenty years after the Ottomans invaded the Balkans, they conquered Sofia, choosing it as their regional capital. The native population, a mix of the original Thracian tribes, Slavs, and Bulgars, was driven to less desirable mountain zones while the Turkish colonists settled on the plain. Turkish Islam ruled Sofia until 1878, making it a center of commerce.

Sofia was declared the capital of the newly autonomous principality of Bulgaria in 1879. The new monarchy proceeded to wipe out much of Ottoman Sofia, making it a modern Christian Orthodox capital city.

For reasons related to Bulgaria's losses in the Balkan Wars, the nation sided with the Axis Powers in World War II. While it did not play a major role, Sofia was bombed heavily by allied air forces. Thousands of buildings were either destroyed or damaged. Thus, much of modern day Sofia was built during the Communist regime.