Lal Sena (1974–1990,[1][3] (meaning Red Army in Hindi) was an organised armed militia of CPIML Liberation in northeastern India, across the terrains of central Bihar, north-west of today's Jharkhand, and a few districts of eastern Uttar Pradesh.

In 1960s, when the Naxalite movement[4] started under the leadership of Communist Party of India (Marxist–Leninist),[5] the poor peasantry and agricultural labourers who belonged mainly to the lower castes started taking side with the communists in central Bihar across the districts of Bhojpur, Gaya, Nalanda, Patna and Aurangabad.

In retaliation Lal Sena guerrilla armed squads, were organised by then underground CPI (ML) Liberation.

The CPI (ML) Liberation party's movements took a militant but democratic approach through legalised workers, peasants, students, youth and women organisations, as noted by Dr. Sanjay K. Jha:[10] "The CPI-ML (Liberation), which had a formidable presence in the central parts of undivided Bihar, decided to function as an over ground political party in 1992.

It was, however, added that the party must prepare itself for winning the ultimate decisive victory through an armed struggle", though it admitted that the situation was not ripe for such a movement.