Chersonesus is an ancient Greek colony founded approximately 2,500 years ago in the southwestern part of the Crimean Peninsula. The colony was established in the 6th century BC by settlers from Heraclea Pontica.

The ancient city is located on the shore of the Black Sea at the outskirts of Sevastopol on the Crimean Peninsula, where it is referred to as Khersones. It has been nicknamed the "Ukrainian Pompeii" and "Russian Troy". The site is now part of the National Historical-Archeological Museum-Zapovednik of the Ukrainian Khersones Tavriysky. The name "Chersonesos" in Greek means "peninsula", and aptly describes the site on which the colony was established. It should not be confused with the Tauric Chersonese, the name often applied to the whole of the southern Crimea.

During much of the classical period Chersonesus was a democracy ruled by a group of elected archons and a council called the Demiurgi. As time passed the government grew more oligarchic, with power concentrated in the hands of the archons. A form of oath sworn by all the citizens since the 3rd century BC has survived to the present day. In 2013, Chersonesus was listed as a World Heritage Site.

In the late 2nd century BC Chersonesus became a dependency of the Bosporan Kingdom. It was subject to Rome from the middle of the 1st century BC until the 370s AD, when it was captured by the Huns.

It became a Byzantine possession during the Early Middle Ages and withstood a siege by the Göktürks in 581. Byzantine rule was slight: there was a small imperial garrison more for the town's protection than for its control. It was useful to Byzantium in two ways: as an observation point to watch the barbarian tribes, and its isolation made it a popular place of exile for those who angered the Roman and later Byzantine governments. Among its more famous "inmates" were Pope Clement I and Pope Martin I, and the deposed Byzantine Emperor Justinian II. According to Theophanes the Confessor and others, Chersonesus was the residence of a Khazar governor (tudun) in the late 7th century.

In 833 Emperor Theophilus sent the nobleman Petronas Kamateros, who had recently overseen the construction of the Khazar fortress of Sarkel, to take direct control over the city and its environs, establishing the theme of Klimata/Cherson. It remained in Byzantine hands until the 980s, when it reportedly fell to Kiev. Vladimir the Great agreed to evacuate the fortress only if Basil II's sister Anna Porphyrogeneta would be given him in marriage. The demand caused a scandal in Constantinople, as imperial princesses had never been married to non-Greeks before. As a pre-condition for the marriage settlement, Vladimir was baptized here in 988, thus paving the way to the Baptism of Kievan Rus'. Thereafter Korsun' was evacuated.

Since this campaign is not recorded in Greek sources, historians have suggested that this account actually refers to the events of the Rus'-Byzantine War (1043) and to a different Vladimir. In fact, most valuables looted by the Slavs in Korsun' made their way to Novgorod (perhaps by way of Ioakim Korsunianin, the first Novgorodian bishop, as his surname indicates ties to Korsun), where they were preserved in the Cathedral of Holy Wisdom until the 20th century. One of the most interesting items from this "Korsun Treasure" is the copper Korsun Gate, supposedly captured by the Novgorodians in Korsun' and now part of the St. Sophia Cathedral.

After the Fourth Crusade Chersonesus became dependent on the Empire of Trebizond, and then fell under Genoese control in the early 13th century. In 1299, the town was sacked by the armies of Nogai Khan.

In 1333 a Latin Church diocese of Chersonnesus was established, but it appears that it had only bishop, a Dominican called Richard the Englishman. No longer a residential bishopric, Chersonnesus in Zechia is today listed by the Catholic Church as a titular see. Chersonnesus had been a Greek episcopal see for centuries, elevated early to the rank of archbishopric, since it is mentioned as such in the Notitiae Episcopatuum; it disappeared after the Turkish conquest in 1475 and the destruction of the city. In the late 19th century, St Vladimir's Cathedral (completed 1892) was built on a small hill overlooking the site; designed in Byzantine style, it was intended to commemorate the site of Vladimir's baptism.

Chersonesus' ancient ruins are presently located in one of Sevastopol's suburbs. They were excavated by the Russian government, starting from 1827. They are today a popular tourist attraction, protected as an archaeological park.

The buildings mix influences of Greek, Roman and Byzantine culture. The defensive wall was approximately 3.5 kilometres (2.2 mi) long, 3.5 to 4 metres wide and 8 to 10 metres high with towers at a height of 10 to 12 metres. The walls enclosed an area of about 30 hectares (74 acres). Buildings include a Roman amphitheatre and a Greek temple.

The surrounding land under the control of the city, the chora, consists of several square kilometres of ancient but now barren farmland, with remains of wine presses and defensive towers. According to archaeologists, the evidence suggests that the locals were paid to do the farm work instead of being enslaved.

The excavated tombstones hint at burial practices that were different from the Greek ones. Each stone marks the tomb of an individual, instead of the whole family and the decorations include only objects like sashes and weapons, instead of burial statues. Over half of the tombs archaeologists have found have bones of children. Burned remnants suggest that the city was plundered and destroyed.

In 2007, Chersonesus tied for fifth in the Seven Wonders of Ukraine poll.

On February 13, 2009, Ukrainian Defence Minister Yuriy Yekhanurov called on Russia's Black Sea naval fleet to move its automobile depot from the site to another place. The location of the Russian Black Sea naval fleet's automobile depot was one of the obstacles to the inclusion of the reserve on UNESCO's list of world heritage sites.

The 1935 Basilica is the most famous basilica excavated in Chersonesus. The original name is unknown so "1935" refers to the year it was opened.[8] The basilica was probably built in the 6th century on the site of an earlier temple, assumed by historians to be a synagogue, itself replacing a small temple dating from the early days of Christianity.[9] The 1935 basilica is often used as an image representing Chersonesos. Its picture appears on one Ukrainian banknote.

As well as the archaeological sites, the museum has around 200,000 smaller items from 5 AD to the 15th century, over 5,000 of which are currently exhibited. These include: ancient texts, including the Oath of Chersonese citizens (3 AD), decrees in honour of Diophantus (2nd Century AD); a collection of coins; a mosaic of black and white pebbles and coloured stones; ancient ceramics; architectural fragments, including ancient and medieval abacuses, reliefs, the remains of ancient murals.