Singapore is a parliamentary republic with a Westminster system of unicameral parliamentary government representing constituencies. Its constitution establishes representative democracy as its political system. Freedom House ranks Singapore as "partly free" in its Freedom in the World report, and The Economist ranks Singapore as a "hybrid regime", the third rank out of four, in its "Democracy Index". Singapore is consistently rated one of the least corrupt countries in the world by Transparency International.

Executive power rests with the Cabinet, led by the Prime Minister, and the President. The president is elected through popular vote, and has some veto powers for a few key decisions such as the use of the national reserves and the appointment of judges, but otherwise occupies a ceremonial post.

The Parliament serves as the legislative branch of government. Members of Parliament (MPs) consist of elected, non-constituency and nominated members. Elected MPs are voted into parliament on a "first-past-the-post" (plurality) basis and represent either single-member or group-representation constituencies. The People's Action Party has won control of Parliament with large majorities in every election since self-governance was secured in 1959. However, in the most recent parliamentary elections in 2011, the opposition, led by the Workers' Party, made significant gains and increased its representation in the House to 6 elected MPs.

The legal system of Singapore is based on English common law, albeit with substantial local differences. Trial by jury was entirely abolished in 1970 leaving judicial assessment performed wholly by judgeship. Singapore has penalties that include judicial corporal punishment in the form of caning for rape, rioting, vandalism, and some immigration offences. There is a mandatory death penalty for murder, and for certain drug-trafficking and firearms offences. Amnesty International has said that some legal provisions conflict with the right to be presumed innocent until proven guilty, and that Singapore has "possibly the highest execution rate in the world relative to its population". The government has disputed Amnesty's claims. In a 2008 survey, international business executives believed Singapore, along with Hong Kong, had the best judicial system in Asia. In 2011, in the World Justice Project's Rule of Law Index Singapore was ranked in the top countries surveyed in "Order and Security", "Absence of Corruption", and "Effective Criminal Justice". However, it scored very low for both "Freedom of Speech" and "Freedom of Assembly". All public gatherings of five or more people require police permits, and protests may only be legally held at Speakers' Corner.