Makassar Strait is a strait between the islands of Borneo and Sulawesi in Indonesia. To the north it joins the Celebes Sea, while to the south it meets the Java Sea. The Mahakam River of Borneo empties into the strait.
Ports along the strait include Balikpapan in Borneo, and Makassar and Palu in Sulawesi. The city of Samarinda is 48 km (30 mi) from the strait, along the Mahakam.
The strait is a common shipping route for oceangoing ships too big to fit through the Straits of Malacca.
Makassar Strait Wikipedia
The International Hydrographic Organization (IHO) defines the Makassar Strait as being one of the waters of the East Indian Archipelago. The IHO defines its limits as follows:
The channel between the East coast of Borneo and the West coast of Celebes [Sulawesi], is bounded:
On the North. By a line joining Tanjong Mangkalihat, Borneo (1°02′N 118°57′E) and Stroomen Kaap (Cape Rivers), Celebes (1°20′N 120°52′E).
On the South. By a line from the Southwestern extreme of Celebes (5°37′S 119°27′E), through the Southern point of Tana Keke, to the Southern extreme of Laoet (4°06′S 116°06′E) thence up the West coast of that island to Tanjong Kiwi and thence across to Tanjong Petang, Borneo (3°37′S 115°57′E) at the Southern end of Laoet Strait.