South China Sea , arm of the western Pacific Ocean that borders the Southeast Asian mainland. It is bounded on the northeast by the Taiwan Strait (by which it is connected to the East China Sea ); on the east by Taiwan and the Philippines; on the southeast and south by Borneo, the southern limit of South China Sea is an arm of the western Pacific Ocean that borders the Southeast Asian mainland. Explore how China ’s claims over the South China Sea have antagonized competing countries and track the latest developments with CFR's Global Conflict Tracker. Overlapping claims in the South China Sea threaten to turn the region into a flashpoint of global concern.