Peninsular Malaysia, also known as Malaya or West Malaysia, is the part of Malaysia which lies on the Malay Peninsula and surrounding islands. Its area is 132,265 square kilometres (51,068 sq mi), which is nearly 40% of the total area of the country – or slightly larger than England (130,395 km²). It shares a land border with Thailand to the north and Singapore at the southernmost tip.

Across the Strait of Malacca to the west lies the Sumatra Island (Indonesia) and across the South China Sea to the east lies the Natuna Islands (Indonesia). 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).

Peninsular Malaysia consists of the following 11 states and two federal territories (starting from the North going to the South):
Northern Region: Perlis, Kedah, Penang, Perak
East Coast Region: Kelantan, Terengganu, Pahang,
Central Region: Selangor, federal territories of Kuala Lumpur and Putrajaya
Southern Region: Negeri Sembilan, Malacca, Johor

SOURCE: https://en.wikipedia.org/wiki/Peninsular_Malaysia