The Parliament of the Democratic Socialist Republic of Sri Lanka (Sinhala: ශ්‍රී ලංකා පාර්ලිමේන්තුව Śrī Laṇkā Pārlimentuvā, Tamil: இலங்கை நாடாளுமன்றம் Ilaṅkai nāṭāḷumaṉṟam) is the supreme legislative body of Sri Lanka. It alone possesses legislative supremacy and thereby ultimate power over all other political bodies in the island. It is modelled after the British Parliament. The 17th Parliament of Sri Lanka convened for the first time on 21 November 2024.

It consists of 225 members known as Members of Parliament (MPs). Members are elected by proportional representation for five-year terms, with universal suffrage.

The President of Sri Lanka has the power to summon, suspend, prorogue, or terminate a legislative session and to dissolve the Parliament. The President can dissolve Parliament only after the lapse of 2+1⁄2 years or if a 2⁄3 majority of the Members of Parliament requests dissolution. The action of the president to either suspend or dissolve the Parliament is subject to legal scrutiny of the Supreme Court of Sri Lanka. The Speaker or, in his absence, the Deputy Speaker and Chairman of Committees or the Deputy Chairman of Committees, presides over Parliament.

The Standing Orders of Parliament are the agreed rules under which procedure, debate, and the conduct of Members in the House are regulated. It defines the procedure for the functioning of Parliament, thus becoming an important source of Parliamentary Procedure. Standing Orders have the status of rules under the Constitution, and date back to the first set of Standing Orders adopted by the Legislative Council of Ceylon in 1912, based those of the Parliament of the United Kingdom. These have been changed multiple times and the current set of Standing Orders dates back to 1979.

Following the Westminster model, all legislation in Sri Lanka must be passed by the Parliament to become law and it controls taxation and the supply of money to the government. Parliament's ability to make laws, includes those that have retrospective effect and repealing or amending any provision of the Constitution, or adding any provision to the Constitution. Government ministers must regularly answer questions in Parliament and there are a number of select committees which scrutinise particular issues and the workings of the government.

Under the Parliament (Powers and Privileges) Act, Parliament and its members are entitled to legal immunity to ensure freedom of speech, freedom from arrest on civil matters and ensure publication of the reports, papers, minutes, votes or proceedings of Parliament. In addition to the privileges laid out in the act, Parliament and its members are entitled to the same parliamentary privilege in the United Kingdom. Parliament and any committee can summon any person or request any record or document to be produced before Parliament or the committee.

The first legislature established in Ceylon was the Executive Council and the legislative council, which were established on 13 March 1833 according to the recommendations of the Colebrook-Cameron commission. The Executive Council was composed of the Colonial Secretary, the officer commanding the Military Forces, the Attorney General, the Auditor-General and the Treasurer. The duties of the council were advisory and the Governor of Ceylon, who presided over their meetings and consulted them, was at liberty to disregard their advice. At first it was made up of only British officials but later included native citizens. At the beginning 16, and later 49 members, were elected for the legislative council, but a limited number of people were qualified to vote.

In 1931 the Legislative Council was dissolved and in its place a more powerful State Council of Ceylon was established, with its 101 members elected by universal adult franchise as provided by the Donoughmore Constitution.