Cattigara is the name of a major port city located on the Magnus Sinus described by various ancient sources. Some modern scholars have linked Cattigara to the archaeological site of Óc Eo in present-day Vietnam.

Cattigara was the name given by the 2nd-century Alexandrian geographer Claudius Ptolemy to the land on the easternmost shore of the Indian Sea at (due to a scribal error) 8½° south of the Equator.

The name "Cattigara" was probably derived from the Sanskrit Kirti-nagara कीर्ति- नगर "Renowned City" or Kotti-nagara कोटि-नगर "Strong City".

On some medieval maps, for example on the Martellus map of 1489 or the Waldseemüller map from 1507, published in the Ptolemy's Geography, Cattigara was located 8 and a half degrees below the equator and 178 degrees west of the Canary Islands.

Guided by Ptolemy, the discoverers of the New World were initially trying to find their way to Cattigara. On the 1489 map of the world made by Henricus Martellus Germanus, revising Ptolemy's work, Asia terminated in its southeastern point in a cape, the Cape of Cattigara. Writing of his 1499 voyage, Amerigo Vespucci said he had hoped to reach Malacca (Melaka) by sailing westward from Spain across the Western Ocean (the Atlantic) around the Cape of Cattigara into the Sinus Magnus ("Great Gulf") that lay to the east of the Golden Chersonese (Malay Peninsula), of which the Cape of Cattigara formed the southeastern point. The Sinus Magnus was the actual Gulf of Thailand.

Christopher Columbus, on his fourth and last voyage of 1502–1503, planned to follow the coast of Ciamba southward around the Cape of Cattigara and sail through the strait separating Cattigara from the New World, into the Sinus Magnus to Malacca. This was the route he thought Marco Polo had gone from China to India in 1292. Columbus planned to meet up with the expedition sent at the same time from Portugal around the Cape of Good Hope under Vasco da Gama, and carried letters of credence from the Spanish monarchs to present to da Gama. On reaching Cariay on the coast of Costa Rica, Columbus thought he was close to the gold mines of Ciamba. On 7 July 1503, he wrote from Jamaica: "I reached the land of Cariay...Here I received news of the gold mines of Ciamba which I was seeking".

It was eventually realized that Columbus had not reached Ciamba or any part of the Cape of Cattigara. The search for Cattigara continued during the early years of the sixteenth century. Johannes Schöner concluded after the circumnavigation of the world by the expedition led by Ferdinand Magellan that the Pacific Ocean was the Sinus Magnus and located Cattigara on the west coast of South America. In this he was followed by Oronce Fine and the makers of the Dieppe Maps but eventually geographers and cartographers had to admit that Cattigara could not be found. The mathematician and cosmographer Gemma Frisius said in 1531: "in the place where Ptolemy described Cattigara as projecting far beyond the Equator, and others by quite dubious reasoning as adjoining the kingdoms of Var, Moabar and other places now, following repeated voyages on both this side and the other of the Equator, no continental land was found but an almost infinite number of islands".

John Caverhill deduced in 1767 that Cattigara was the Mekong Delta port Banteaymeas (between modern-day Banteay Meas District and Hà Tiên), not far from Óc Eo. The plea in 1979 by Jeremy H.C.S. Davidson for "a thorough study of Hà-tiên in its historical context and in relation to Óc-eo" as indispensable for an accurate understanding and interpretation of the site, still remains unanswered.