Selatan Strait (South Strait), also known as Penang Strait and "South Channel", is the channel that separates Penang Island from mainland Peninsular Malaysia. The mainland side, known as Seberang Perai, forms the strait's eastern side, while the east coast of Penang Island forms its western side. The north and south ends of the strait join the Strait of Malacca, the world's busiest sea route.