Sofia Airport (IATA: SOF, ICAO: LBSF) (Bulgarian: Летище София, Letishte Sofiya), sometimes also called Letishte Sofia-Vrazhdebna (Bulgarian: Летище София-Враждебна, Letishte Sofiya-Vrazhdebna), is the main airport in Sofia, Bulgaria. It is 5 km (3.1 mi) east of central Sofia. In 2011 the airport served 3.474 million passengers. Sofia airport includes the Vrazhdebna Air Base of the Bulgarian Air Force.

The airport was initially built in the late 1930s on a site 6.3 km (3.9 mi) (7.5 km (4.7 mi) by road then; later 9 km (5.6 mi) by road and today 10.2 km (6.3 mi) and up to 11.4 km (7.1 mi)) distant from the geographical centre of Sofia as a replacement of that city's small civil airport at Bozhurishte. Sofia then had under 250,000 inhabitants. The airport continues to serve the same city, which had about 1.2 million by 2011.

During the Second World War, the facilities were used by the military. Mail, perishable freight and passenger operations began in 1947 from buildings on the north side of the airport. The passenger terminal (now Terminal 1) on the south side was completed during the Second World War in the manner of a then-modern European railway terminus to designs by the architect Ivan Marangozov. It opened after several years of delay in 1947. The structure comprised a government wing to the west, an international handling area in the middle, and a domestic handling area to the east. At that time, it was planned that the airport would eventually have two intersecting runways at a 30-degree angle to each other.

Sofia (Bulgarian: София, pronounced [ˈsɔfijɐ] ( listen)) is the capital and largest city of Bulgaria and the 15th largest city in the European Union with a population of 1.2 million people. It is located in western Bulgaria, at the foot of Mount Vitosha and approximately at the centre of the Balkan Peninsula.

Prehistoric settlements were excavated in the centre of the present city, near the royal palace, as well as in outer districts Slatina and Obelya. The well-preserved town walls (especially their substructures) date back before the 7th century BC, when Thracians established their city around a mineral spring, which exists to the present day. Sofia has had several names in the different periods of its existence. Its ancient name, Serdika or Serdica, derives from the local Celtic tribe of the serdi who inhabited the region since the 1st century BC. Serdica was a Roman capital during the tetrarchic system of government. During the Middle Ages, it was one of the major commercial centres of the Bulgarian Empire, along with Tarnovo. Sofia's population remained small until 1879, when it was declared a capital of the Principality of Bulgaria after the Liberation of Bulgaria from Ottoman rule.