Indonesia–Singapore relations are foreign bilateral relations between Republic of Indonesia and Republic of Singapore. The two countries established formal diplomatic relations on 7 September 1967, a month after the formation of the Association of Southeast Asian Nations (ASEAN) on 8 August 1967. Indonesia and Singapore are two of the five founding members of ASEAN (including Malaysia, Thailand, Philippines). Both nations are also members of the Non-Aligned Movement and APEC.
Over the years, Indonesia and Singapore have maintained regular exchanges of high-level visits, underpinned by strong economic cooperation across a wide range of sectors, including health, defence and the environment. In the past decade, Singapore has consistently been Indonesia's top foreign investor.
2017 mark the 50th anniversary of their diplomatic relations in a celebration event known as RISING50, an amalgamation of “RI” for the Republic of Indonesia and “SING” for Singapore. 
The relations between ancient Indonesia and Singapore dated back from the period of ancient kingdoms, the straits region was part of Srivijaya’s realm back in 7th century. The Nagarakretagama, a Javanese epic poem written in 1365 during Majapahit era, also referred to a settlement on the island called Temasek ('Sea Town' in Old Javanese, spelt Tumasik).
In the 1390s, a Palembang prince, Parameswara, fled to Temasek after being deposed by the Majapahit kingdom. During the 14th century, Singapore was caught in the struggle between Siam (now Thailand) and the Java-based Majapahit Empire for control over the Malay Peninsula. According to Sejarah Melayu, Singapore was defeated in one Majapahit attack. He ruled the island for several years, before being forced to Melaka where he founded the Sultanate of Malacca.
In early 19th century, Singapore was under British control as Straits Settlements and later as Crown colony, while at the same period Indonesian archipelago gradually fell under control of Dutch East Indies Company and Dutch East Indies.
After the independence of Indonesia in 1945 and the separation of Singapore from Malaysia in 1965, both countries opened bilateral diplomatic ties on 1966. In 1967, they founded ASEAN together with Thailand, Philippines and Malaysia, to strive for peace and stability in the region. Formal diplomatic relations was established between Singapore and Indonesia on 7 September 1967.
50th anniversary of formal diplomatic relations
The golden jubilee of Indonesia-Singapore diplomatic relations was marked by a series of events in August: A "four-eye" meeting between the two leaders, RISING50 book launch, joint commemorative stamps issue, tree-planting at the Singapore Botanic Gardens. The first ever combined flypast of 20 fighter jets from the Republic of Singapore Air Force (RSAF) and Tentara Nasional Indonesia-Angkatan Udara (TNI-AU) was also held, in a formation of the number "50". On the economic front, an investment forum was held and nine memoranda of understandings(MOUs) were signed, including cooperations in education and research, student exchanges, environment and energy.
Trade and commerce
Located on the busiest sea lane in Straits of Malacca, serving as one of world's main hub, trade with and through Singapore is important for Indonesia to provide the link to trade with the rest of the world. Vice versa, Indonesian business is also important for Singapore. Trade and commerce is the main common motivation of both nations foreign relations, each counterpart are main trade partners of each other.
Indonesia-Singapore trade volume reaches S$36 billion (US$29.32 billion). Singapore is Indonesia's top foreign investor, with a cumulative total of US$1.14 billion in 142 projects. Trade between the two countries also hit around $68 billion in 2010. At the same time, Indonesia's non-oil and gas exports to Singapore are the highest in the region.
Other than business purposes, Indonesian visitors attracted to Singapore mostly for shopping, city sightseeing, and island resorts with its theme parks, zoos, museums and gardens. While Singaporeans attracted to Indonesia mostly for its nature and culture, Bali and neighboring Batam island are particularly popular among Singapore visitors.
Security, counter terrorism and border
On 3 October 2005, Prime Minister Lee Hsien Loong met Indonesian President Susilo Bambang Yudhoyono in Bali, just two days after the Bali bombings. They agreed to strengthen the fight against terrorism and also discussed cooperation in the fields of economy, trade, energy and investment.
Territorial and environment issues
Singapore scarcity of land and spaces have led them to expand their island through land reclamations. The materials needed for reclamation, sands and granites, are mostly imported from Indonesia. The quarry of sands from Indonesian territories has raised concern over environmental issues.
In June 2013, Singapore suffers the haze coming from slash-and-burn practice to clear plantation lands in neighboring Riau, Sumatra, Indonesia. The June 2013 haze hit the worst record, reaching the highest haze pollutant levels since 1997. The haze has prompted a health alert from the Singaporean government, angered Singaporean citizens and also caused some diplomatic tension as the Singaporean government protested Indonesia's tardiness at handling the issue and urged the Indonesian government to look for effective measures to mitigate the transboundary haze pollution occurrence.
In addition, there has also been differences between both countries on the administration of the Riau Islands Flight Information Region (FIR). Singapore has generally claimed that it controls the FIR based on an arrangement made by the International Civil Aviation Organization, and that it is a matter of aviation safety and efficiency.  However, some past and present Indonesian officials have argued against Singapore's right to do so, and reasoned that the FIR is a critical determinant of Indonesia's air sovereignty and defense. While the matter does not appear to compromise bilateral relations significantly, arguments from both sides are raised from time to time.
- Indonesia–Singapore border
- Indonesia–Malaysia–Singapore Growth Triangle
- Riau Islands Flight Information Region
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