East Malaysia in the context of "Western Indonesia"

Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania, between the Indian and Pacific oceans. Comprising over 17,000 islands, including Sumatra, Java, Sulawesi, and parts of Borneo and New Guinea, Indonesia is the world's largest archipelagic state and the 14th-largest country by area, at 1,904,569 square kilometres (735,358 square miles). With over 280 million people, Indonesia is the world's fourth-most-populous country and the most populous Muslim-majority country. Java, the world's most populous island, is home to more than half of the country's population.

Indonesia operates as a presidential republic with an elected legislature and consists of 38 provinces, nine of which have special autonomous status. Jakarta, the largest city, is the world's second-most-populous urban area. Indonesia shares land borders with Papua New Guinea, Timor-Leste, and East Malaysia, as well as maritime borders with Singapore, Peninsular Malaysia, Vietnam, Thailand, the Philippines, Australia, Palau, and India. Despite its large population and densely populated regions, Indonesia has vast areas of wilderness that support one of the world's highest levels of biodiversity.

The Malay Archipelago is the archipelago between Mainland Southeast Asia and Australia, and is also called Insulindia or the Indo-Australian Archipelago. The name was taken from the 19th-century European concept of a Malay race, later based on the distribution of Austronesian languages. It has also been called the "Malay world", "Nusantara", and the "East Indies" over time. The name is controversial in Indonesia due to its ethnic connotations and colonial undertones, which can overshadow the country's diverse cultures.

Situated between the Indian and Pacific oceans, the archipelago of over 25,000 islands and islets is the largest archipelago by area and fifth by number of islands in the world. It includes Brunei, East Timor, Indonesia, Malaysia (specifically East Malaysia), Papua New Guinea, the Philippines, and Singapore. The term is largely synonymous with Maritime Southeast Asia.

Malaysia is a country in Southeast Asia. A federal constitutional monarchy, it consists of 13 states and three federal territories, separated by the South China Sea into two regions: Peninsular Malaysia on the Indochinese Peninsula and East Malaysia on the island of Borneo. Peninsular Malaysia shares land and maritime borders with Thailand, as well as maritime borders with Singapore, Vietnam, and Indonesia; East Malaysia shares land borders with Brunei and Indonesia, and maritime borders with the Philippines and Vietnam. Kuala Lumpur is the country's national capital, largest city, and the seat of the legislative branch of the federal government, while Putrajaya is the federal administrative capital, representing the seat of both the executive branch (the Cabinet, federal ministries, and federal agencies) and the judicial branch of the federal government. With a population of over 34 million, it is the world's 42nd-most populous country.

The country has its origins in the Malay kingdoms, which, from the 18th century on, became subject to the British Empire, along with the British Straits Settlements protectorate. During World War II, British Malaya, along with other nearby British and American colonies, was occupied by the Empire of Japan. Following three years of occupation, Peninsular Malaysia was briefly unified as the Malayan Union in 1946 until 1948 when it was restructured as the Federation of Malaya. The country achieved independence on 31 August 1957. On 16 September 1963, independent Malaya united with the then British crown colonies of North Borneo, Sarawak, and Singapore to become Malaysia. In August 1965, Singapore was expelled from the federation and became a separate, independent country.

Malaya, officially the Federation of Malaya, was a country in Southeast Asia from 1948 to 1963. It succeeded the Malayan Union and, before that, British Malaya. It comprised eleven states – nine Malay states and two of the Straits Settlements, Penang and Malacca. It was established on 1 February 1948.

Initially a self-governing colony of the United Kingdom, Malaya became fully sovereign on 31 August 1957, and on 16 September 1963, Malaya was superseded by Malaysia when it united with Singapore, North Borneo (Sabah) and Sarawak. Singapore was expelled on 9 August 1965, leaving the original states of Malaya along with Sarawak and Sabah – now collectively known as East Malaysia – to form modern-day Malaysia, while the former Federation of Malaya is now referred to as Peninsular Malaysia or West Malaysia.

The history of Southeast Asia covers the people of Southeast Asia from prehistory to the present in two distinct sub-regions: Mainland Southeast Asia (or Indochina) and Maritime Southeast Asia (or Insular Southeast Asia). Mainland Southeast Asia comprises Cambodia, Laos, Myanmar (or Burma), Peninsular Malaysia, Thailand and Vietnam whereas Maritime Southeast Asia comprises Brunei, Cocos (Keeling) Islands, Christmas Island, East Malaysia, East Timor, Indonesia, Philippines and Singapore.

The earliest Homo sapiens presence in Mainland Southeast Asia can be traced back to 70,000 years ago and to at least 50,000 years ago in Maritime Southeast Asia. Since 25,000 years ago, East Asian-related (basal East Asian) groups expanded southwards into Maritime Southeast Asia from Mainland Southeast Asia. As early as 10,000 years ago, Hoabinhian settlers from Mainland Southeast Asia had developed a tradition and culture of distinct artefact and tool production. During the Neolithic, Austroasiatic peoples populated Mainland Southeast Asia via land routes, and sea-borne Austronesian immigrants preferably settled in Maritime Southeast Asia. The earliest agricultural societies that cultivated millet and wet-rice emerged around 1700 BCE in the lowlands and river floodplains of Southeast Asia.

Peninsular Malaysia, historically known as Peninsular Malaya or simply Malaya prior to 1963, and also known as West Malaysia and the Malaysian Peninsula, is the southern part of the Malay Peninsula in Mainland Southeast Asia along with the nearby islands that are part of Malaysia. Its area totals approximately 131,956 km (50,948 sq mi). It makes up nearly 40% of the total area of Malaysia; the other 60% is on the island of Borneo, also known as East Malaysia.

The present-day land border with Thailand to the north originates from the Anglo–Siamese Treaty of 1909, while a maritime border with Singapore to the south was established following the independence of Singapore in 1965. To the west, across the Strait of Malacca, lies the island of Sumatra, and to the east, across the South China Sea, lie the Natuna Islands, both part of Indonesia. At its southern tip, across the Strait of Johor, lies the island country of Singapore. Most of Peninsular Malaysia's interior is forested, mountainous and rural, while the majority of the population and economic activity are concentrated along the coastal western half, where the country's major urban centres are located.

Malaysia is a federation of thirteen states and three federal territories, which form the primary administrative divisions of the country. Eleven states and two territories are part of Peninsular Malaysia, while two states and one territory make up East Malaysia. Nine of the Peninsular states have monarchies, with the other four having appointed governors. State governments are led by chief ministers, who are appointed by the monarch or governor, provided they have the support of a majority in the state legislative assembly. The federal territories are governed directly by the national government.

Malaysia was formed through the union of various territories ruled by the United Kingdom in British Malaya and British Borneo. The federal system was created to maintain the status of the Malay sultans, who were the rulers of British protectorates in the Malay Peninsula. The Federation of Malaya was created in 1948, uniting these protectorates with two directly ruled British colonies. Malaya became independent in 1957. In 1963, Sabah and Sarawak, along with Singapore, joined with Malaya to form Malaysia. Singapore was expelled in 1965. The three federal territories–Kuala Lumpur, Labuan and Putrajaya–were created later, from land separated from existing states.

Independence Day (Malay: Hari Merdeka), also known as National Day (Malay: Hari Kebangsaan), is the independence day of the Federation of Malaya from the United Kingdom. It commemorates the Malayan Declaration of Independence of 31 August 1957, and is defined in article 160 of the Constitution of Malaysia. The day is marked by official and unofficial ceremonies and observances across the country.

The observation of 31 August as Malaysia's national day is the cause of some controversy, especially among East Malaysians, with calls to prioritise the celebration of Malaysia Day (Hari Malaysia) on 16 September instead. Malaysia Day commemorates the formation of Malaysia in 1963, when the four entities of North Borneo, Sarawak, Singapore and Malaya federated to form Malaysia as part of the Malaysia Agreement.

Malaysia Day (Malay: Hari Malaysia) is a public holiday observed nationwide on 16 September each year since 2010. It marks the anniversary of the signing of the Malaysia Agreement, which came into effect on that date in 1963 and led to the creation of Malaysia. The agreement brought together the Malaya (independent since 1957), North Borneo (later renamed Sabah), Sarawak and Singapore into a single federation. Singapore was later expelled from the federation on 9 August 1965, and Malaysia Day is no longer observed there.

In East Malaysia, many regard Malaysia Day as the country's true "national day", arguing that 31 August commemorates the independence of Malaya, which was a separate political entity to Malaysia.