As traditionally the oldest form of Christianity, along with the ancient or first millennial Eastern Orthodox Church, the non-Chalcedonian or Oriental Churches, and the Church of the East, the history of the Catholic Church is integral to the history of Christianity as a whole. It is also, according to church historian, Mark A. Noll, the "world's oldest continuously functioning international institution." This article covers a period of just under two thousand years

Abhisit Vejjajiva (; Thai: อภิสิทธิ์ เวชชาชีวะ, RTGS: Aphisit Wetchachiwa, [ʔà.pʰí.sìt wêːt.tɕʰāː.tɕʰīː.wáʔ]; born 3 August 1964) is a British Thai politician who was the prime minister of Thailand from 2008 to 2011. He is a former university lecturer at Chulachomklao Royal Military Academy and Thammasat University, and was the leader of the Democrat Party from 2005 until he resigned following the party's weak performance in the 2019 election. As leader of the second largest party in the House of Representatives, he was also leader of the opposition – a position he held from December 2008 until his party's en masse resignation from the House on 8 December 2013. That same month, he was formally charged with murder resulting from a crackdown on demonstrators in 2010 that killed 90 people. Born in England, the United Kingdom, Abhisit attended Eton College and earned bachelor's and master's degrees from the University of Oxford. He was elected to the Parliament of Thailand at the age of 27, and promoted to Democrat Party leader in 2005, after his predecessor resigned following the party's defeat in the 2005 general election. Abhisit was appointed prime minister of Thailand on 17 December 2008, after the Constitutional Court of Thailand removed Prime Minister Somchai Wongsawat from office. At age 44, he was the country's youngest prime minister in more than 60 years. Abhisit became premier at a time of global economic turmoil and rising domestic political tensions. As prime minister, he promoted a "People's Agenda," which focused primarily on policies affecting the living conditions of Thailand's rural and working class citizens. He administered two economic stimulus packages: a US$40 billion, three-year infrastructure improvement plan, and a more than US$3 billion program of cash subsidies and handouts. By 2010, the stock market and the value of the baht had rebounded to their highest levels since the 1997 Asian Financial Crisis. Human Rights Watch called Vejjajiva "the most prolific censor in recent Thai history" and Freedom House downgraded Thailand's rating of media freedom to "not free." Abhisit also advocated for stronger anti-corruption measures, although several members of his Cabinet resigned due to corruption scandals and parts of his economic stimulus packages were criticised for instances of alleged corruption. Abhisit's government faced major protests in April 2009 and April–May 2010. The military's crackdowns on protesters left many dead. Abhisit launched a reconciliation plan to investigate the crackdown, but the work of the investigation commission was hampered by military and government agencies. The Thai Army clashed with Cambodian troops numerous times from 2009 to 2010 in the bloodiest fighting in over two decades. The South Thailand insurgency escalated during Abhisit's government, and reports of torture and human rights violations increased. Having resigned the party leadership after the defeat the Democrats suffered in the parliamentary elections of 2011, Abhisit was re-elected as leader at a party assembly. In 2018, the Democrats held a contest for party leader in preparation for the upcoming election. Abhisit was re-elected party leader, beating former PDRC leader, Warong Dechgitvigrom, by approximately 10,000 votes. However, after a poor showing in the 2019 election, Abhisit resigned as party leader.
Abhisit Vejjajiva (; Thai: อภิสิทธิ์ เวชชาชีวะ, RTGS: Aphisit Wetchachiwa, [ʔà.pʰí.sìt wêːt.tɕʰāː.tɕʰīː.wáʔ]; born 3 August 1964) is a British Thai politician who was the prime minister of Thailand from 2008 to 2011. He is a former university lecturer at Chulachomklao Royal Military Academy and Thammasat University, and was the leader of the Democrat Party from 2005 until he resigned following the party's weak performance in the 2019 election. As leader of the second largest party in the House of Representatives, he was also leader of the opposition – a position he held from December 2008 until his party's en masse resignation from the House on 8 December 2013. That same month, he was formally charged with murder resulting from a crackdown on demonstrators in 2010 that killed 90 people.

As traditionally the oldest form of Christianity, along with the ancient or first millennial Eastern Orthodox Church, the non-Chalcedonian or Oriental Churches, and the Church of the East, the history of the Catholic Church is integral to the history of Christianity as a whole. It is also, according to church historian, Mark A. Noll, the "world's oldest continuously functioning international institution." This article covers a period of just under two thousand years Over time, schisms have disrupted the unity of Christianity. The major divisions occurred in c.144 with Marcionism, 318 with Arianism, 451 with the Oriental Orthodox, 1054 to 1449 (see East–West Schism) during which time the Orthodox Churches of the East parted ways with the Western Church over doctrinal issues (see the filioque) and papal primacy, and in 1517 with the Protestant Reformation, of which there were many divisions, resulting in over 200 denominations. This Church has been the driving force behind some of the major events of world history including the Christianization of Western and Central Europe and Latin America, the spreading of literacy and the foundation of the universities, hospitals, the Western tradition of monasticism, the development of art and music, literature, architecture, contributions to the scientific method, just war theory and trial by jury. It has played a powerful role in global affairs, including the Reconquista, the Crusades, the Inquisition, the Investiture Controversy, the establishment of the Holy Roman Empire, and the Fall of Communism in Eastern Europe in the late 20th century.