Which sea lies east of Vietnam and west of the Philippines?

The sea east of Vietnam and west of the Philippines is the South China Sea.

The South China Sea is a marginal sea of the western Pacific Ocean. Vietnam and the Indochinese Peninsula form much of its western boundary, while Taiwan and the northwestern Philippines—including Luzon, Mindoro, and Palawan—mark its eastern side. Its position makes it a natural answer to the geographic description in the question.

The sea covers roughly 3.5 million square kilometres and connects with nearby waters through several straits. The Taiwan Strait links it with the East China Sea, the Luzon Strait with the Philippine Sea, and passages around Palawan with the Sulu Sea. These neighboring seas are common distractors because they are all part of the same interconnected region.

The name is politically sensitive. China commonly calls it the South Sea, Vietnam calls it the East Sea, and the Philippines uses West Philippine Sea for portions within its maritime jurisdiction. Despite these differing names and competing territorial claims, “South China Sea” remains the standard international geographic name for the larger body of water.