Luis Crisologo Singson (born June 21, 1941), better known as Chavit Singson, is a Filipino politician. He was a former Governor of the province of Ilocos Sur, Philippines since 1998. He ran for the Senate in the 2007 Elections in the Philippines but he lost greatly. He returned again as governor of Ilocos Sur, prior to his re-election in 2010.

Chavit Singson was born on June 21, 1941 in Vigan City, Ilocos Sur. He is the second among the seven children of José Singson and Caridad Crisólogo. His other siblings, aside from Evaristo (Titong), are Bernardo (deceased), Fernando (Dodoy), Maria Olivia (Honeygirl), Jeremias (Jerry), Germelina (Germy) and Jose, Jr. (Bonito).

Singson's growing-up years were spent in Vigan, where he led a normal childhood "with a very liberal upbringing and a lot of opportunity to play and make friends." He apparently got his own fondness for jueteng from his mother who loved the game. Despite their prominence in the province, it was not always a life of wealth for the Singsons. At one point, the family had to sell their appliances. Singson learned how difficult life was without money. Singson's character was strengthened especially with the seemingly unending family squabbles and political dynasties of his youth, the tobacco industry in Ilocos and how the Singsons got into tobacco growing and trading. The family brought the first redrying plant to Ilocos in the '60s.

Both his paternal (Singson) and maternal (Crisologo) families have dominated the political environment of the Ilocos region for generations. Although many members of both families, such as Chavit are related to one another, the two families have shared a bitter feud which reached its apex in the 1960s and 1970s, when shootings and political intimidation were rampant in the Ilocos region. Chavit considered his uncle, Floro Crisologo as a mentor, but eventually had a severe falling out with his cousin and once-confidant Vicente "Bingbong" Crisologo (who was Floro's son) and there were many bloody encounters between the two. It is currently stated by both sides that tensions have eased.

Singson started out as a businessman .He then entered politics, becoming a political kingpin in his province for 28 years, and later playing a significant role in Philippine politics and democracy. He is the former (2004–2007) Governor of Ilocos Sur a position he has held for 50 years.

Singson currently lives in his home, called Baluarte, in Vigan City. He is a former close friend and gambling and drinking buddy of President Estrada. Singson was married to Evelyn Verzosa on May 3, 1962, but later separated. They had seven children.

Singson later cohabited with Rachel "Che" Tiongson, with whom he has five children. In early September 2009, he was charged with assaulting Tiongson and her boyfriend. Singson insisted that he caught Tiongson and her unidentified boyfriend in flagrante delicto, in her own apartment. Tiongson, on the other hand, insists that she and Singson have long separated.

Commission on Human Rights (CHR) chair Leila De Lima on September 5, 2009 assailed deputy National Security Adviser Luis Singson for his "arrogance" and urged his common-law wife Rachel 'Che' Tiongson to file a human rights complaint.

In an interview with ABS-CBN News, de Lima lamented Singson's statement in media interviews, including with dzMM and ABS-CBN News, that Tiongson and her boyfriend should be thankful he did not kill them for their affair.

Singson had secured a spot as a candidate for the 2007 Philippine senatorial elections. He has sided with the government party, despite being former friends with the former president Joseph Estrada. After losing the elections, Singson had been appointed Deputy National Security Adviser, on September 5, 2008 by Gloria Macapagal Arroyo.