The Sympathizer is the 2015 debut novel by Vietnamese-American professor and writer Viet Thanh Nguyen. It is a best-selling novel, and recipient of the 2016 Pulitzer Prize for Fiction. The novel received positive reviews from critics. It was named on more than 30 best book of the year lists and a New York Times Editor's Choice.

The novel incorporates elements from a number of different novel genres: mystery, political, metafiction, dark comedic, historical, spy, and war. The story depicts the anonymous narrator, a North Vietnamese mole in the South Vietnamese army, who stays embedded in a South Vietnamese community in exile in the United States. While in the United States, the narrator describes being an expatriate and a cultural advisor on the filming of an American film, closely resembling Platoon and Apocalypse Now, before returning to Vietnam as part of a guerrilla raid against the communists.

The dual identity of the narrator, as a mole and immigrant, and the Americanization of the Vietnam War in international literature are central themes in the novel. The novel was published 40 years to the month after the fall of Saigon, which is the initial scene of the book.

The novel was adapted as a television series of the same name, which premiered in April 2024, produced by A24 for HBO Max.

A sequel, titled The Committed, was published on March 2, 2021.

Set as the flashback in a coerced confession of a political prisoner, the narrator describes the South Vietnamese Government in 1975 and subsequent events in American exile in Los Angeles through the eyes of a half-Vietnamese, half-French undercover communist agent. The spy remains unnamed throughout the novel from the fall of Saigon, to refugee camps and relocation in Los Angeles, to his time as a film consultant in the Philippines, and finally to his return and subsequent imprisonment in Vietnam.

The narrator lives in a series of dualities, at times contradictions: he is of mixed blood descent (Vietnamese mother, and French Catholic priest father), raised in Vietnam but attended college in the U.S., and a North Vietnamese mole yet a friend to South Vietnamese military officials and soldiers and a United States CIA agent. During the imminent fall of Saigon, he, as an aide-de-camp, arranges for a last minute flight as part of Operation Frequent Wind, to secure the safety of himself, his best friend Bon, and the General he advises. While they are being evacuated, the group is fired upon while boarding; during the escape, Bon's wife and child are killed along with many others.

In Los Angeles, the General and his former officers weaken quickly, disillusioned by a foreign culture and their rapid decline in status. The General attempts to reclaim some semblance of honor by opening his own business, a liquor store. The continuous emasculation and dehumanization within American society prompts the General to draft plans for assembling an army of South Vietnamese expatriates to return as rebels to Vietnam. While participating in the expatriate unit, the narrator takes a clerical position at Occidental College, begins having an affair with Ms. Mori, his Japanese-American colleague, and then the General's eldest daughter, Lana. While living in the United States, the narrator sends letters in invisible ink to Man, a North Vietnamese revolutionary and handler, providing intelligence about the General's attempts at raising a commando army.