Tết Nguyên Đán pronunciation (help·info) (Sino-Vietnamese for Feast of the First Morning, derived from Hán nôm 節元旦), more commonly known by its shortened name Tết, is the most important holiday in Vietnam. It is the Vietnamese New Year which is based on the Chinese calendar, a lunisolar calendar.Tet is the most popular festival in Vietnam and artifacts suggest that it has been celebrated since at least 500 B. C. E. The exact origin is unknown.

Tết is celebrated on the same day as Chinese New Year though exceptions arise due to the 1 hour time difference between Hanoi and Beijing. Tết share many of the same customs of its Chinese counterpart. It is celebrated from the first day of the first month of the Chinese calendar (around late January or early February) until at least the third day. Many Vietnamese prepare for Tết by cooking special holiday foods and cleaning the house. On Tết, Vietnamese visit their families and temples, forget about the troubles of the past year and hope for a better upcoming year. Tết traditionally marks the coming of Spring, so Spring is sometimes used interchangeably with Tết in Vietnamese. Nowadays, the term "Tet" in English often refers to the bloody Tết Offensive, which occurred during Tết in 1968.