Peninsular Malaysia (Malay: Semenanjung Malaysia), also known as Malaya or West Malaysia, is the part of Malaysia which occupies the southern half of the Malay Peninsula and the surrounding islands. Its area is 132,265 square kilometres (51,068 sq mi), which is nearly 40% of the total area of the country; the other 60% is East Malaysia. For comparison, it is slightly larger than England (130,395 km²). It shares a land border with Thailand to the north.
Across the Strait of Malacca to the west lies the island of Sumatra (Indonesia) and across the South China Sea to the east lies the Natuna Islands (Indonesia). At the southern tip across the Strait of Johor lies the island and country of Singapore. Peninsular Malaysia accounts for the majority (roughly 81.3%) of Malaysia's population and economy; as of 2017 its population is roughly 26 million (92% of total population).
The majority of people on Peninsular Malaysia are ethnic Malays, predominantly Muslim. Large Chinese and Indian populations exist. The Orang Asli are the indigenous people of Peninsular Malaysia; they number around 140,000 and mostly live in inland parts of the region.
The term West Coast refers informally to a collection of states in Peninsular Malaysia situated towards the western coast generally facing the Strait of Malacca which is a component of the Indian Ocean, as opposed to the East Coast. Unlike the East Coast, the West Coast is partitioned further into three regions (as seen in #States and territories), including:
Even though Johor has a coastline facing the South China Sea on the Pacific Ocean, it is not generally regarded as an East Coast state, since the main coastline of the state is located on the Straits of Johor of the Indian Ocean.
The distinction between West and East Malaysia (Sabah and Sarawak) goes beyond the sphere of geography. Being separate regions administratively before the formation of the Malaysia, there exists more autonomy than the original States of Malaya, e.g. in having a different judicial court structure and separate immigration regulations. These rights were granted as part of Sarawak's 18-point agreement and Sabah's 20-point agreement with the Federation of Malaya during the formation of expanded federation.