Sri Lanka (UK: , US: (listen); Sinhala: , romanized: r Lak (IPA: [ri laka]); Tamil: , romanized: Ilakai (IPA: [ilaaj])), formerly known as Ceylon and officially the Democratic Socialist Republic of Sri Lanka, is an island country in South Asia. It lies in the Indian Ocean, southwest of the Bay of Bengal, and southeast of the Arabian Sea; it is separated from the Indian subcontinent by the Gulf of Mannar and the Palk Strait. Sri Lanka shares a maritime border with India and the Maldives. Sri Jayawardenepura Kotte is its legislative capital, and Colombo is its largest city and financial centre.

Sri Lanka's documented history goes back 3,000 years, with evidence of prehistoric human settlements that dates to at least 125,000 years ago. It has a rich cultural heritage. The earliest known Buddhist writings of Sri Lanka, known collectively as the Pli canon, date to the fourth Buddhist council, which took place in 29 BCE. Also called the Teardrop of India, or the Granary of the East, Sri Lanka's geographic location and deep harbours have made it of great strategic importance, from the earliest days of the ancient Silk Road trade route to today's so-called maritime Silk Road. Because its location made it a major trading hub, it was already known to both Far Easterners and Europeans as long ago as the Anuradhapura period. The country's trade in luxury goods and spices attracted traders of many nations, which helped to create Sri Lanka's diverse population. During a period of great political crisis in the Sinhalese kingdom of Kotte, the Portuguese arrived in Sri Lanka (largely by accident) and then sought to control the island's maritime regions and its lucrative external trade. Part of Sri Lanka became a Portuguese possession. After the Sinhalese-Portuguese war, the Dutch and the Kingdom of Kandy took control of those areas. The Dutch possessions were then taken by the British, who later extended their control over the whole island, colonising it from 1815 to 1948. A national movement for political independence arose in the early 20th century, and in 1948, Ceylon became a dominion. The dominion was succeeded by the republic named Sri Lanka in 1972. Sri Lanka's more recent history was marred by a 26-year civil war, which began in 1983 and ended decisively in 2009, when the Sri Lanka Armed Forces defeated the Liberation Tigers of Tamil Eelam.Today, Sri Lanka is a multinational state, home to diverse cultures, languages, and ethnicities. The Sinhalese are the majority of the nation's population. The Tamils, who are a large minority group, have also played an influential role in the island's history. Other long established groups include the Moors, the Burghers, the Malays, the Chinese, and the indigenous Vedda.The island has had a long history of engagement with modern international groups: it is a founding member of the SAARC and a member of the United Nations, the Commonwealth of Nations, the G77, and the Non-Aligned Movement. Sri Lanka is the highest-ranked South Asian nation on the Human Development Index and has the second-highest per capita income in South Asia; however, the ongoing economic crisis has resulted in the collapse of the currency, rising inflation, and a humanitarian crisis due to a severe shortage of essentials. It has also led to an eruption of street protests, with citizens demanding that the President and the government step down.

A constitution is an aggregate of fundamental principles or established precedents that constitute the legal basis of a polity, organisation or other type of entity and commonly determine how that entity is to be governed.When these principles are written down into a single document or set of legal documents, those documents may be said to embody a written constitution; if they are encompassed in a single comprehensive document, it is said to embody a codified constitution. The Constitution of the United Kingdom is a notable example of an uncodified constitution; it is instead written in numerous fundamental Acts of a legislature, court cases or treaties.Constitutions concern different levels of organizations, from sovereign countries to companies and unincorporated associations. A treaty which establishes an international organization is also its constitution, in that it would define how that organization is constituted. Within states, a constitution defines the principles upon which the state is based, the procedure in which laws are made and by whom. Some constitutions, especially codified constitutions, also act as limiters of state power, by establishing lines which a state's rulers cannot cross, such as fundamental rights.

The Constitution of India is the longest written constitution of any country in the world, with 146,385 words in its English-language version, while the Constitution of Monaco is the shortest written constitution with 3,814 words. The Constitution of San Marino might be the world's oldest active written constitution, since some of its core documents have been in operation since 1600, while the Constitution of the United States is the oldest active codified constitution. The historical life expectancy of a constitution since 1789 is approximately 19 years.