Óc Eo (Vietnamese) is an archaeological site in modern-day Óc Eo commune of Thoại Sơn District in An Giang Province of southern Vietnam. Located in the Mekong Delta, Óc Eo was a busy port of the kingdom of Funan between the 2nd century BC and 12th century AD and it may have been the port known to the Greeks and Romans as Cattigara.

Scholars use the term Óc Eo culture to refer to the archaeological culture of the Mekong Delta that is typified by the artifacts recovered at Óc Eo through archaeological investigation.

Excavation at Óc Eo began on 10 February 1942, after French archaeologists had discovered the site through the use of aerial photography. The first excavations were led by Louis Malleret, who identified the site as the place called Cattigara by Roman merchants in the first centuries of the Roman Empire. The site covers 450 hectares.

Óc Eo is situated within a network of ancient canals that crisscross the low flatland of the Mekong Delta. One of the canals connects Óc Eo to the town's seaport while another goes 68 kilometres (42 mi) north-northeast to Angkor Borei. Óc Eo is longitudinally bisected by a canal, and there are four transverse canals along which pile-supported houses were perhaps ranged.

Archaeological sites reflecting the material culture of Óc Eo are spread throughout southern Vietnam, but are most heavily concentrated in the area of the Mekong Delta to the south and west of Ho Chi Minh City. The most significant site, aside from Óc Eo itself, is at Tháp Muời north of the Tiền Giang River, where among other remains a stele with a 6th-century Sanskrit text has been discovered.

Aerial photography in 1958 revealed that a distributary of the Mekong entered the Gulf of Thailand during the Funan period in the vicinity of Ta Keo, which was then on the shore but since then become separated from the sea by some distance as a result of siltation. At that time, Ta Keo was connected by a canal with Óc Eo, allowing it access to the Gulf. The distributary of the Mekong revealed in the aerial photography was probably the Saenus mentioned in Ptolemy’s Geography as the western branch of the Mekong, which Ptolemy called the Cottiaris. The Cattigara in Ptolemy's Geography could be derived from a Sanskrit word, either Kottinagara (Strong City) or Kirtinagara (Renowned City).

The remains found at Óc Eo include pottery, tools, jewelry, casts for making jewelry, coins, and religious statues. Among the finds are gold jewellery imitating coins from the Roman Empire of the Antonine period. Roman golden medallions from the reign of Antoninus Pius, and possibly his successor Marcus Aurelius, have been discovered at Óc Eo, which was near Chinese-controlled Jiaozhou and the region where Chinese historical texts claim the Romans first landed before venturing further into China to conduct diplomacy in 166. Many of the remains have been collected and are on exhibition in Museum of Vietnamese History in Ho Chi Minh City.

Among the coins found at Óc Eo by Malleret were eight made of silver bearing the image of the hamsa or Vietnamese crested argus, apparently minted in Funan.

In July 2023, a stone slab that is roughly the size and shape of an anvil was discovered at Óc Eo, marking the earliest known example of spice processing in Southeast Asia.

Óc Eo has been regarded as belonging to the historical kingdom of Funan (扶南) that flourished in the Mekong Delta between the 2nd century BC and the 12th century CE. The kingdom of Funan is known to us from the works of ancient Chinese historians, especially writers of dynastic histories, who in turn drew from the testimony of Chinese diplomats and travellers, and of foreign (including Funanese) embassies to the Chinese imperial courts. Indeed, the name "Funan" itself is an artifact of the Chinese histories, and does not appear in the paleographic record of ancient Vietnam or Cambodia. From the Chinese sources, however, it can be determined that a polity called "Funan" by the Chinese was the dominant polity located in the Mekong Delta region. As a result, archeological discoveries in that region that can be dated to the period of Funan have been identified with the historical polity of Funan. The discoveries at Óc Eo and related sites are our primary source for the material culture of Funan.

The Vietnamese archaeologist and historian Hà Văn Tấn has written that at the present stage of knowledge, it was impossible to demonstrate the existence of a Funan culture, widely spread from the Mekong Delta through the Chao Praya delta to Burma, with Óc Eo as the typical representative: the presence of similar artefacts such as jewelry and seals from sites in those areas was simply the result of trade and exchange, while each of the sites bore the signs of their own separate cultural development. He supported the view of Claude Jacques that, in view of the complete lack of any Khmer records relating to a kingdom by the name of Funan, use of this name should be abandoned in favour of the names, such as Aninditapura, Bhavapura, Shresthapura and Vyadhapura, which are known from inscriptions to have been used at the time for cities in the region and provide a more accurate idea of the true geography of the ancient Khmer territory. Hà Văn Tấn argued that, from the late neolithic or early metal age, Óc Eo gradually emerged as an economic and cultural centre of the Mekong Delta and, with an important position on the Southeast Asian sea routes, became a meeting place for craftsmen and traders, which provided adequate conditions for urbanization, receiving foreign influences, notably from India, which in turn stimulated internal development.

Funan was part of the region of Southeast Asia referred to in ancient Indian texts as Suvarnabhumi, and may have been the part to which the term was first applied.

Part of a series on
Prehistoric and ancient cultures of Vietnam
Paleolithic
Sơn Vi culture (20,000–12,000 BC)
Mesolithic
Hoabinhian (12,000–10,000 BC)
Neolithic
Bắc Sơn culture (10,000–8,000 BC) Quỳnh Văn culture (8,000–6,000 BC) Đa Bút culture (4,000–3,000 BC)
Bronze Age
Phùng Nguyên culture (2,000–1,500 BC) Đồng Đậu culture (1,500–1,000 BC) Gò Mun culture (1,000–800 BC) Dong Son culture (1,000 BC–100 AD)
Iron Age
Sa Huỳnh culture (1,000 BC–200 AD) Óc Eo culture (1–630 AD)
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