The flag of Singapore was adopted in 1959, the year Singapore became self-governing within the British Empire. Designed by a government committee led by deputy prime minister Toh Chin Chye, it remained as the national flag upon the country's independence from Malaysia on 9 August 1965. The design is a horizontal bicolour of red above white, overlaid in the canton (upper hoist quarter) by a white crescent moon facing a pentagon of five small white five-pointed stars. The elements of the flag denote a young nation on the ascendant, universal brotherhood and equality, and national ideals.
Vessels at sea do not use the national flag as an ensign. Merchant vessels and pleasure craft fly a civil ensign of red charged in white with a variant of the crescent and stars emblem in the centre. Non-military government vessels such as coast guard ships fly a state ensign of blue with the national flag in the canton, charged with an eight-pointed red and white compass rose in the lower fly. Naval ships patrol a naval ensign similar to the state ensign, but in white with a red compass rose emblem.
The usage and exhibition of the national flag in Singapore are regulated by the rules set forth in the National Symbols Act. Under the Act, which took effect on 1 August 2023 and superseded the former Singapore Arms and Flag and National Anthem Act, private citizens may include the flag in designs for other objects, and the national flag or its image can be used on attire above the torso for non-commercial purposes year-round as long as it is not done in a disrespectful manner. Regulations are relaxed during National Day celebrations from 1 July to 30 September.
Singapore was under British rule in the 19th century, having been amalgamated into the Straits Settlements together with Malacca and Penang. The flag that was used to represent the Settlements was a British Blue Ensign defaced with a red diamond containing three gold crowns—one for each settlement—separated by a white inverted pall, which resembles an inverted Y. The Settlement of Singapore had no separate flag, although the city was granted a coat of arms which featured a lion in 1911. During the occupation of Singapore by the Japanese during the Second World War, the Japanese national flag was used on land by the military and during public events. Soon after the Second World War, Singapore became an independent Crown colony and adopted its own flag. It was modified from the Straits Settlements flag to reduce the number of crowns from three to one. Upon Queen Elizabeth II's accession to the throne, the crown within the pall was changed to the crown of St. Edward.
Singapore became self-governing within the British Empire on 3 June 1959. Six months later, upon the installation of the new Yang di-Pertuan Negara Yusof Ishak on 3 December 1959, the national flag was officially adopted, along with the state coat of arms and the national anthem "Majulah Singapura" (lit. 'Onward Singapore'). Then-deputy prime minister Toh Chin Chye discussed the creation of the national flag in a 1989 interview:
Although we were self governing it was necessary right from the beginning that we should rally enough different races together as a Singapore nation... Apart from the anthem we have to produce the flag and the crest, we insisted that it was a Singapore state flag and should be flown side by side with the Union Jack.
The design of the flag and crest was completed in two months by a committee headed by Toh. He initially wanted the flag's entire background to be red, but the Cabinet decided against this, as red was regarded as a rallying point for communism. Toh had opposed a red-and-white design as he considered it too similar to the flags of Indonesia and Poland, but the proposals for all-red, all-blue or blue-and-white designs were rejected. The flag, according to Toh, originally had only three stars (representing democracy, justice, and equality), but two more stars and a crescent were added later to distance it from the Malayan Communist Party emblem and to assure the Malay-Muslim community that Singapore was "not a Chinese state". According to an account given by Lee Kuan Yew, the Chinese majority wanted stars based on the flag of the People's Republic of China while the Malay minority wanted a crescent moon to represent Islam. Both of these symbols were combined to create the national flag of Singapore.
On 30 November 1959, the Singapore State Arms and Flag and National Anthem Ordinance 1959 was passed to regulate the use and display of the State Arms and State Flag and the performance of the National Anthem. When presenting the motion to the Legislative Assembly of Singapore on 11 November 1959, culture minister Sinnathamby Rajaratnam stated: "National flags, crest and anthem express symbolically the hopes and ideals of a people... The possession of a national flag and crest is, for a people, symbolic of self-respect." In September 1962, the people of Singapore voted for merger with Malaya, Sarawak, and North Borneo to form Malaysia. The process was completed on 16 September 1963, when the Malaysian flag was hoisted on Singapore by prime minister Lee. The Singapore flag was reconfirmed as the national flag when Singapore became fully independent from Malaysia on 9 August 1965.
The National Symbols Act defines the flag's composition and the symbolism of its elements: red symbolises "universal fellowship and equality", and white symbolises "pervading and everlasting purity and virtue". The crescent moon represents a "young nation on the ascendant". The five stars stand for the nation's ideals of "democracy, peace, progress, justice and equality". The crescent symbol is also seen by the nation's Muslim activists to represent Islam.
The ratio of the flag is two units high by three units wide. For the manufacturing of flags, the Government of Singapore stated that the shade of red used on the flag is Pantone 032. According to guidelines published by the Ministry of Information, Communications and the Arts (MICA), the flag may be reproduced in any size and displayed at all times, but it must be in its specified proportions and colours. MICA recommends the sizes 915 by 1,370 mm (36 by 54 in), 1,220 by 1,830 mm (48 by 72 in), and 1,830 by 2,740 mm (72 by 110 in). The material that is recommended for the national flag is bunting wool.
The Singaporean government dictates that no person may treat the national flag with disrespect, such as allowing the flag to touch the ground. The flag must not be displayed below any other flag, emblem, or object; dipped in salute to any person or thing; or displayed or carried flat or horizontally, but always aloft and free. The use and display of the flag is governed by the National Symbols Act (until 2023 governed by Part III of the Singapore Arms and Flag and National Anthem Rules made under the Singapore Arms and Flag and National Anthem Act). It was an offence to knowingly contravene specified provisions of the Singapore Arms and Flag and National Anthem Rules; the penalty was a fine not exceeding S$1,000.
Within Singapore, the national flag takes precedence over all other flags, subject to international practice. As such, when it is displayed or flown with other flags, it must be in a position of honour; that is, it should be positioned, where practical, either above all other flags or, if displayed side by side with other flags on the same level, to the left of the other flags (as seen by a person facing the flags). When the flag is raised or carried in a procession with other flags, it must be done so in front of the other flags in a single file, or on the right as seen by the standard bearers if the flags are carried side by side (i.e., on the left as seen by the viewer). The standard bearer must carry the flag high on his or her right shoulder.
When the flag is displayed on a platform or stage, it must be above all decorations and be behind and above any person speaking from the platform or stage. If it is displayed from a staff standing on the platform or stage, it must be on the right side of the person speaking from the platform or stage. Finally, when the flag is hung, it must be hung against a vertical wall or other vertical flat surface, with the crescent and stars on the top left position as seen by any spectator facing the flag and the wall or surface.