Tarakan is an island and co-extensively the sole city within the Indonesian province of North Kalimantan. The island city is the largest urban area in North Kalimantan population-wise and is located in northern Borneo, midway along the coast of the province. The city boundaries are co-extensive with the island. Once a major oil-producing region during the colonial period, Tarakan had great strategic importance during the Pacific War and was among the first Japanese targets early in the conflict. It is the sole city within the newly established Indonesian province of North Kalimantan. According to Statistics Indonesia, the city had a population of 193,370 at the 2010 Census and 242,786 inhabitants at the 2020 Census; the official estimate as at mid 2023 was 249,960.

The Celebes Sea or Sulawesi Sea of the western Pacific Ocean is bordered on the north by the Sulu Archipelago and Sulu Sea and Mindanao Island of the Philippines, on the east by the Sangihe Islands chain, on the south by Sulawesi's Minahasa Peninsula, and the west by northern Kalimantan in Indonesia. It extends 420 miles (675 km) north-south by 520 mi (840 km) east-west and has a total surface area of 110,000 square miles (280,000 km2), to a maximum depth of 20,300 feet (6,200 m). South of the Cape Mangkalihat, the sea opens southwest through the Makassar Strait into the Java Sea.