Nesebar (often transcribed as Nessebar and sometimes as Nesebur, Bulgarian: Несебър, pronounced [nɛˈsɛbɐr]) is an ancient city and one of the major seaside resorts on the Bulgarian Black Sea Coast, located in Burgas Province. It is the administrative centre of the homonymous Nesebar Municipality. Often referred to as the "Pearl of the Black Sea", Nesebar is a rich city-museum defined by more than three millennia of ever-changing history. The small city exists in two parts separated by a narrow human-made isthmus with the ancient part of the settlement on the peninsula (previously an island), and the more modern section (i.e., hotels and later development) on the mainland side. The older part bears evidence of occupation by a variety of different civilisations over the course of its existence.

It is one of the most prominent tourist destinations and seaports on the Black Sea, in what has become a popular area with several large resorts—the largest, Sunny Beach, is situated immediately to the north of Nesebar.

Nesebar has on several occasions found itself on the frontier of a threatened empire, and as such it is a town with a rich history. Due to the city's abundance of historic buildings, UNESCO came to include Nesebar in its list of World Heritage Sites in 1983.

As of December 2019, the town has a population of 13,600 inhabitants.