Pompeii is a vast archaeological site in southern Italy's Campania region, near the coast of the Bay of Naples. Once a thriving and sophisticated Roman city, Pompeii was buried under meters of ash and pumice after the catastrophic eruption of Mount Vesuvius in 79 A.D. The preserved site features excavated ruins of streets and houses that visitors can freely explore.

Pompeii was an ancient Roman city near modern Naples in the Campania region of Italy, in the territory of the commune of Pompei. Pompeii, along with Herculaneum and many villas in the surrounding area (e.g. at Boscoreale, Stabiae), was buried under 4 to 6 m (13 to 20 ft) of volcanic ash and pumice in the eruption of Mount Vesuvius in AD 79. Many of the inhabitants were also buried before they could escape.

Largely preserved under the ash, the excavated city offers a unique snapshot of Roman life, frozen at the moment it was buried and providing an extraordinarily detailed insight into the everyday life of its inhabitants. During excavations liquid plaster was used to fill voids in the ash that once held organic remains including wood, human and animal bodies, giving unique and often gruesome images of their last moments. The numerous graffiti carved on the walls and inside rooms provides a wealth of information regarding Vulgar Latin spoken colloquially rather than that of the classical writers.

Pompeii is a UNESCO World Heritage Site status and is one of the most popular tourist attractions in Italy, with approximately 2.5 million visitors every year.

Excavations recommenced in several unexplored areas of the city and in 2018 new discoveries were reported.

Pompeii in Latin according to Theodor Kraus, "The root of the word Pompeii would appear to be the Oscan word for the number five, pompe, which suggests that either the community consisted of five hamlets or, perhaps, it was settled by a family group."

The ruins of Pompeii are located near the modern town of Pompei and about 5.0 mi away from Mount Vesuvius. It stands on a spur about 40 m above sea level formed by an ancient lava flow to the north of the mouth of the Sarno River (known in ancient times as the Sarnus). Three sheets of sediment from large landslides lie on top of the lava, perhaps triggered by extended rainfall.

Today, Pompeii is some distance inland but in ancient times was overlooking the coast and had a port. It covered a total of 170 acres and was home to 11,000 to 11,500 people on the basis of household counts.

By the 1st century AD, Pompeii was one of a number of towns near the base of the volcano, Mount Vesuvius. The area had a substantial population, which had grown prosperous from the region's renowned agricultural fertility. Many of Pompeii's neighboring communities, most famously Herculaneum, also suffered damage or destruction during the 79 eruption.

A multidisciplinary volcanological and bio-anthropological study of the eruption products and victims, merged with numerical simulations and experiments, indicates that at Pompeii and surrounding towns heat was the main cause of death of people, previously believed to have died by ash suffocation. The results of the study, published in 2010, show that exposure to at least 482 degrees F hot surges, known as pyroclastic flows at a distance of 6 miles from the vent was sufficient to cause instant death, even if people were sheltered within buildings. The people and buildings of Pompeii were covered in up to 12 different layers of tephra, in total 82 ft deep, which rained down for about six hours.

Pliny the Younger provided a first-hand account of the eruption of Mount Vesuvius from his position across the Bay of Naples at Misenum but written 25 years after the event. His uncle, Pliny the Elder, with whom he had a close relationship, died while attempting to rescue stranded victims. As admiral of the fleet, Pliny the Elder had ordered the ships of the Imperial Navy stationed at Misenum to cross the bay to assist evacuation attempts. Volcanologists have recognized the importance of Pliny the Younger's account of the eruption by calling similar events "Plinian". It had long been thought that the eruption was an August event based on one version of the letter but another version gives a date of the eruption as late as 23 November. A later date is consistent with a charcoal inscription at the site, discovered in 2018, which includes the date of 17 October and which must have been recently written.

Further support for an October/November eruption is found in the fact that people buried in the ash appear to have been wearing heavier clothing than the light summer clothes typical of August. The fresh fruit and vegetables in the shops are typical of October - and conversely the summer fruit typical of August was already being sold in dried, or conserved form. Wine fermenting jars had been sealed, which would have happened around the end of October. Coins found in the purse of a woman buried in the ash include one with a 15th imperialist acclamation among the emperor's titles. These coins could not have been minted before the second week of September.

Soon after the burial of the city some surviving owners or thieves came to collect materials or valuables including marble statues from buildings. They left traces of their passage, as in a house where modern archaeologists found a wall graffitus saying "House dug".  During the following centuries, its name and location was forgotten. The first recorded time any part was unearthed was in 1592, when the digging of an underground channel to divert the river Sarno ran into ancient walls covered with paintings and inscriptions. The architect Domenico Fontana was called in; he unearthed a few more frescoes, then covered them over again, and nothing more came of the discovery. A wall inscription had mentioned a decurio Pompeii ("the town councillor of Pompeii") but its reference to the long-forgotten Roman city was missed.

Fontana's covering over the paintings has been seen both as a broad-minded act of preservation for later times, and as censorship in view of the frequent sexual content of such paintings, as he would have known that paintings of the hedonistic kind later found in some Pompeian villas were not considered in good taste in the climate of the counter-reformation.

Herculaneum was properly rediscovered in 1738 by workmen digging for the foundations of a summer palace for the King of Naples, Charles of Bourbon. Pompeii was rediscovered as the result of intentional excavations in 1748 by the Spanish military engineer Rocque Joaquin de Alcubierre. Charles of Bourbon took great interest in the findings even after becoming king of Spain because the display of antiquities reinforced the political and cultural power of Naples.

Karl Weber directed the first real excavations; he was followed in 1764 by military engineer Franscisco la Vega. Franscisco la Vega was succeeded by his brother, Pietro, in 1804. During the French occupation Pietro worked with Christophe Saliceti.

Giuseppe Fiorelli took charge of the excavations in 1863. During early excavations of the site, occasional voids in the ash layer had been found that contained human remains. It was Fiorelli who realized these were spaces left by the decomposed bodies and so devised the technique of injecting plaster into them to recreate the forms of Vesuvius's victims. This technique is still in use today, with a clear resin now used instead of plaster because it is more durable, and does not destroy the bones, allowing further analysis.

The discovery of erotic art in Pompeii and Herculaneum left the archaeologists with a dilemma - between the mores of sexuality in ancient Rome and in Counter-Reformation Europe lay a clash of cultures. An unknown number of discoveries were hidden away again for showing too much. A wall fresco depicting Priapus, the ancient god of sex and fertility, was covered with plaster. An older reproduction was locked away "out of prudishness" and opened only on request-and only rediscovered in 1998 due to rainfall. In 2018, an ancient fresco depicting an erotic scene of "Leda and the Swan" was discovered at Pompeii.

A large number of artifacts from the buried cities are preserved in the Naples National Archaeological Museum. In 1819, when King Francis visited the Pompeii exhibition there with his wife and daughter, he was so embarrassed by the erotic artwork that he decided to have it locked away in a so-called "secret cabinet" (gabinetto segreto), a gallery within the museum accessible only to "people of mature age and respected morals". Re-opened, closed, re-opened again and then closed again for nearly 100 years, the Naples "Secret Museum" was briefly made accessible again at the end of the 1960s and was finally re-opened for viewing in 2000. Minors are still allowed entry only in the presence of a guardian or with written permission.

Pompeii has been a popular tourist destination for over 250 years; it was on the Grand Tour. By 2008, it was attracting almost 2.6 million visitors per year, making it one of the most popular tourist sites in Italy. It is part of a larger Vesuvius National Park and was declared a World Heritage Site by UNESCO in 1997. To combat problems associated with tourism, the governing body for Pompeii, the Soprintendenza Archaeological di Pompei, have begun issuing new tickets that allow for tourists to also visit cities such as Herculaneum and Stabiae as well as the Villa Poppaea, to encourage visitors to see these sites and reduce pressure on Pompeii.

Pompeii is also a driving force behind the economy of the nearby town of Pompei. Many residents are employed in the tourism and hospitality business, serving as taxi or bus drivers, waiters or hotel operators. The ruins can be easily reached on foot from Pompei Scavi-Villa dei Misteri station by Circumvesuviana commuter rail Naples - Sorrento route, directly at the ancient site. There are also car parks nearby.

Excavations in the site have generally ceased due to the moratorium imposed by the superintendent of the site, Professor Pietro Giovanni Guzzo. Additionally, the site is generally less accessible to tourists, with less than a third of all buildings open in the 1960s being available for public viewing today. Nevertheless, the sections of the ancient city open to the public are extensive, and tourists can spend several days exploring the whole site.

Objects buried beneath Pompeii were well-preserved for almost 2,000 years. The lack of air and moisture let objects remain underground with little to no deterioration. Once excavated, the site provided a wealth of source material and evidence for analysis, giving detail into the lives of the Pompeiians. However, once exposed, Pompeii has been subject to both natural and man-made forces, which have rapidly increased deterioration.

Weathering, erosion, light exposure, water damage, poor methods of excavation and reconstruction, introduced plants and animals, tourism, vandalism and theft have all damaged the site in some way. Two-thirds of the city has been excavated, but the remnants of the city are rapidly deteriorating.

The concern for conservation has continually troubled archaeologists. The ancient city was included in the 1996 World Monuments Watch by the World Monuments Fund, and again in 1998 and in 2000. In 1996 the organization claimed that Pompeii "desperately need[ed] repair" and called for the drafting of a general plan of restoration and interpretation. The organization supported conservation at Pompeii with funding from American Express and the Samuel H. Kress Foundation.

Today, funding is mostly directed into conservation of the site; however, due to the expanse of Pompeii and the scale of the problems, this is inadequate in halting the slow decay of the materials. An estimated $335 million is needed for all necessary work on Pompeii.  A recent study has recommended an improved strategy for interpretation and presentation of the site as a cost-effective method of improving its conservation and preservation in the short term.

In June 2013 UNESCO declared: If restoration and preservation works 'fail to deliver substantial progress in the next two years,' Pompeii could be placed on the List of World Heritage in Danger.