Singapore's foreign policy is directed to maintaining a secure environment in Southeast Asia as well as the surrounding territories. An underlying principle is political and economic stability in the region. It has diplomatic relations with 175 other sovereign states. As one of the five founding members of the Association of South East Asian Nations (ASEAN), the country is a strong supporter of the ASEAN Free Trade Area and the ASEAN Investment Area, because Singapore's economic growth is closely linked with the economic progress of the region as a whole. Former Prime Minister Goh Chok Tong proposed the formation of an ASEAN Economic Community, a step beyond the current AFTA bringing it closer to a common market. This idea was agreed to in 2007 for implementation by 2015. Other regional organisations are also important to Singapore, and it is the host of the APEC Secretariat. Singapore also maintains membership in other regional organisations, such as Asia-Europe Meeting, the Forum for East Asia-Latin American Cooperation, and the East Asia Summit. It is also a member of the Non-Aligned Movement and the Commonwealth.

In general, bilateral relations with other ASEAN members are strong; however, disagreements have arisen, and relations with neighbouring Malaysia and Indonesia have historically sometimes been very strained and difficult. Malaysia and Singapore have clashed over the delivery of fresh water to Singapore, access of the Singapore Armed Forces to Malaysian airspace, the sovereignty of Pedra Branca, and the relocation of Tanjong Pagar railway station, among others. Border issues exist with both Malaysia and Indonesia, and both have banned the sale of marine sand to Singapore over disputes about Singapore's land reclamation. Some previous disputes have been resolved by the International Court of Justice. Piracy in the Malacca Strait has been a cause of concern for all three countries. Close economic ties exist with Brunei, and the two share a pegged currency value.

The first diplomatic contact with China was made in the 1970s, with full diplomatic relations being established in the 1990s. Since then the two countries have enjoyed a strong relationship, being major players in strengthening the ASEAN–China relationship. Singapore and the United States share a long-standing and strong relationship, in particular in defence, the economy, health and education. The United States was Singapore's third largest trading partner in 2010, behind the European Union and China. The two countries have a free-trade agreement, and Singapore views its relationship with the United States as an important counterbalance to China's influence. A Strategic Framework Agreement between the two signed in 2005 formalises security and defence cooperation. Singapore has pushed regional counter-terrorism initiatives, with a strong resolve to deal with terrorists inside its borders. To this end it has given support to the US-led coalition to fight terrorism, with bilateral cooperation in counter-terrorism and counter-proliferation initiatives, and joint military exercises.