Some historical references to the National Liberation Front include:
- GREECE. This was the primary underground group providing Greek resistance during World War II. (It's Greek name was the Ethniko Apeleftherotiko Metopo, or EAM.) One of its primary subgroups was the Communist Party of Greece (KKE), whose leaders included Georgios Siantos and Nikolas Zachariadis.
- ALBANIA. This group (aka National Liberation Movement) was also a resistance organization during World War II. One of its more well known leaders was Myslym Peza.
- YEMEN. Founded in the 1960s, this anti-Royalist organization attempted to gain control of Saudi Arabia following Great Britain's departure from the area.
- Other countries with similar NLF organizations included Yugoslavia, El Salvador, Nepal, New Caledonia, India, The Phillipines, Angola, Burundi, Corsica, Bahrain, Kurdistan, Macedonia, Peru, Ethiopia, Nicaragua, and Uganda.
It really depends when and where you are referring to in this question, as the name National Liberation Front is very common in history.
Usually, in American history, we are referring to the Vietcong rebels in South Vietnam during the Vietnam War from 1964 - 1973. They were also sometimes called the National Liberation Army.
Then you have an independence group in 1960s Algeria with the same name, and a later political party in that country. Also, the Sandinistas in Nicaragua were referred to as the National Liberation Front, depending on how exactly you translate the Spanish to English and even an organization for the independence of the Ogaden Somalis carries the name NLF.