Abhisit Vejjajiva ( English pronunciation (help·info); Thai: อภิสิทธิ์ เวชชาชีวะ, RTGS: Aphisit Wetchachiwa, IPA: , born 3 August 1964) is the 27th and current Prime Minister of Thailand. He has been the leader of the Democrat Party since February 2005. Abhisit successfully ran for MP in Bangkok under the Democrat Party following the 1991 NPKC military coup. Abhisit quickly rose through party ranks but failed in a bid to become party leader in 2001. He became party leader after the Party's overwhelming defeat in the 2005 elections.

During the 2005-2006 Thai political crisis, Abhisit asked the then care taker Prime Minister Thaksin Shinawatra to resign so that Article 7 of the 1997 Constitution can be invoked. Abhisit boycotted the 2006 elections, claiming that they "diverted public attention" from Thaksin's sale of Shin Corp. Abhisit voiced displeasure at the 2006 coup that overthrew Thaksin, but otherwise did not protest it or the military junta that ruled Thailand for over a year. A fact-finding panel at the Attorney-General's Office found that the Democrat Party bribed other parties to boycott the 2006 elections to force a constitutional crisis, and voted to dissolve the party. The new Constitutiuonal Court acquitted Abhisit and the Democrats of the vote fraud charges, while banning Thaksin's Thai Rak Thai party for other charges. Abhisit supported the junta's 2007 Constitution, calling it an improvement on the 1997 Constitution. The Democrat Party lost the junta-administered 2007 election to the People's Power Party.

In the crisis that followed, some Democrat Party members acting on their own join People's Alliance for Democracy, which seized Government House, Don Muang Airport, and Suvarnabhumi Airport, while facing violent clashes by the police and anti-PAD protesters. On 19 December 2008, Abhisit voiced displeasure at sieges, but did not stop his deputies from their roles in the PAD because they were merely acting on rights which guarantee by the constitution. The sieges ended after the Constitutional Court banned the People's Power Party. Army commander and co-leader of the 2006 coup, General Anupong Paochinda, allegedly coerced several PPP MPs, including those from the Friends of Newin Group, to defect to the Democrat Party allowing Abhisit to be elected Prime Minister.