Phú Quốc, the Island of a Thousand Names: Chronicle of a Disputed Sovereignty

Off the coast of the Gulf of Thailand, a teardrop-shaped island holds centuries of rivalry, colonial line-drawing, and quiet diplomacy. Today a Vietnamese tourist paradise, Phú Quốc still carries, beneath its white-sand beaches, the layered history of a territory once claimed by two nations.

Aerial view of Phú Quốc's beaches

An Island at the Crossroads of Empires

Seen from above, Phú Quốc looks like an emerald set in the turquoise waters of the Gulf of Thailand, a short distance from the Cambodian coast. But this seemingly timeless beauty conceals a complex political geography. For centuries, the island sat at the edge of two worlds: that of the Khmer Empire, whose influence once extended across much of the Mekong Delta and the Gulf, and that of the rising Vietnamese kingdoms and principalities pushing southward.

In the 17th century, the island briefly fell within the orbit of a Chinese-Cambodian principality, before being settled and durably administered by Vietnamese colonists. It was this continuous presence — this settlement and de facto administration dating back to the imperial era — that would shape the island's status for the following three centuries, laying the groundwork for a territorial dispute that would not be resolved until the dawn of the 21st century.

The Shadow of French Colonization

The 20th century brought its share of administrative upheaval. In 1939, with all of Indochina under French administration, Governor-General Jules Brévié drew a line that would bear his name: the "Brévié Line." This maritime demarcation, conceived primarily as a tool of administrative convenience rather than a definitive border, placed Phú Quốc under the jurisdiction of Cochinchina — that is, Vietnam — while the surrounding seabed and certain nearby islets remained under Cambodian administration.

This compromise, drawn up in the offices of the colonial administration, would become one of the most persistent points of friction between Cambodia and Vietnam once the colonial era ended. The Brévié Line, designed for practical purposes, was never meant to definitively settle the question of island sovereignty.

Sihanouk and the 1967 Recognition

In post-independence Cambodia, the question of Koh Tral — the Cambodian name for Phú Quốc — remained a sensitive subject, carrying strong symbolic weight for part of Khmer public opinion. It was in this context that a decisive diplomatic gesture came in 1967: Prince Norodom Sihanouk issued a declaration officially recognizing the territorial integrity of Vietnam within its existing borders — borders that included Phú Quốc.

This gesture, driven as much by regional geopolitical considerations as by a desire to stabilize relations with Vietnam, did not immediately end the tensions. But it marked an important milestone in the international recognition of the island's status.

1999: The Final Chapter of a Long-Standing Dispute

It would take until the end of the century for the matter to be definitively closed. After decades of negotiations, punctuated by diplomatic tensions and periods of wider regional conflict, Cambodia formally accepted Vietnam's sovereignty over Phú Quốc in 1999. This agreement, part of the broader demarcation of land and maritime borders between the two countries, settled the question of the island's ownership in the Gulf of Thailand.

Since then, Phú Quốc has been fully integrated into Vietnam's administrative map, today established as an island city within Kiên Giang province.

A Memory Written in Sand

Today, visitors strolling the beaches of Bãi Sao or exploring the night markets of Dương Đông are often unaware of this long diplomatic saga. And yet the story remains alive in Cambodian collective memory, where the name Koh Tral still evokes, for some, a piece of lost heritage.

Phú Quốc thus illustrates a reality found across much of Southeast Asia: territories shaped as much by population movement and de facto administration as by borders arbitrarily inherited from colonial rule. One island, two memories — and a sovereignty that is today uncontested under international law, yet whose echo continues to resonate in the national narratives on both sides of the Gulf of Thailand.