Singapore Strait

The Singapore Strait is a waterway stretching 113 kilometers in length and 19 kilometers in width. It connects the Strait of Malacca to its west with the South China Sea to its east. To the north lies Singapore, while the Indonesian Riau Islands sit to the south. The maritime border between these two countries runs through the strait.

This channel includes Keppel Harbour and numerous small islands. It serves as the deepwater route to the Port of Singapore, resulting in heavy traffic. In 2017, roughly 2,000 merchant ships passed through its waters each day. The strait’s depth sets the maximum draft for vessels navigating the Malacca Strait, defining the Malaccamax ship classification.

Historical records show that in the 9th century AD, the Muslim writer Ya’qubi mentioned a “Sea of Salahit”—derived from the Malay word *selat* for strait—as one of the Seven Seas on the route to China. Some scholars link this to Singapore, though others identify it as the Malacca Strait, a meeting point between Arabs and the Zābaj (likely Sumatra). Early European travelers to Southeast Asia sometimes used “Strait of Singapore” to refer to the entire Malacca Strait or its southern portion, as well as other waterways. Historians have also used the plural “Singapore Straits” to describe three or four distinct passages in old texts and maps: the Old Strait of Singapore between Sentosa and Telok Blangah, the New Strait of Singapore southwest of Sentosa, the “Governor’s Strait” or “Strait of John de Silva” (matching Phillip Channel), and the Tebrau Strait. Today, the Singapore Strait refers to the main channel south of Singapore, where the international boundary between Singapore and Indonesia lies.

In 1953, the International Hydrographic Organization defined the strait’s limits. The western boundary aligns with the eastern limit of the Malacca Strait, from Tanjong Piai (the southern tip of the Malay Peninsula) through The Brothers to Klein Karimoen. The eastern boundary runs from Tanjong Datok (the southeast point of Johore) via Horsburgh Reef to Pulo Koka (the northeastern extreme of Bintan Island). The northern boundary follows the southern shore of Singapore Island, Johore Shoal, and the southeastern coast of the Malay Peninsula. The southern boundary connects Klein Karimoen to Pulo Pemping Besar, then along the northern coasts of Batam and Bintan Islands to Pulo Koka.

Pilot guides and charts for the Malacca and Singapore straits have been published for a long time due to the straits’ nature. During the Second World War, the British mined the strait.

In terms of incidents, the Maersk Kendal ran aground on the Monggok Sebarok reef in 2009. In 2024, ReCAAP noted that the targeted theft of engine spares by pirates was unique to the Singapore and Malacca Straits, suggesting a possible black market. In 2025, the International Maritime Bureau’s Piracy Reporting Centre reported a major increase in piracy in the Singapore Straits, including boardings and violent armed robberies of cargo ships. That year, over 60% of global piracy occurred in these waters.