Johor, also spelled Johore, state of Malaysia, southernmost state of Peninsular (West) Malaysia. Its 250-mile (400-km) coastline along the Strait of Malacca and South China Sea also winds around the Republic of Singapore’s northern border and is dotted with small islands. Johor is generally flat and jungle covered, with large swamps, but rises in the east-central region to peaks of over 3,000 feet (900 metres).