The Flag of Singapore was adopted in 1959, the year Singapore became self-governing within the British Empire. It remained 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-left quadrant) 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 warships fly a naval ensign similar to the state ensign, but in white with a red compass rose emblem.

Rules defined by the Singapore Arms and Flag and National Anthem Act govern the use and display of the national flag. Private citizens are allowed to incorporate the flag into designs for other objects from 1 July to 30 September, so long as the action is not disrespectful.