The Revolutionary United Front, or RUF, was a rebel army that fought a failed ten-year insurrection in Sierra Leone starting in 1991 and ending in 2002. The war is estimated to have cost the lives of between 50,000 and 200,000 people.

Led by Foday Sankoh, the RUF developed a reputation for enormous cruelty during its decade-long struggle. The RUF made extensive use of child soldiers, using horrific methods to numb their new recruits to barbarity. Thousands of abducted boys and girls were forced to serve as soldiers or as prostitutes, and those chosen to be fighters were sometimes forced to murder their parents. Guerillas frequently carved the initials "RUF" on their chests, and officers reportedly rubbed cocaine into open cuts on their troops to make them manic and fearless. For entertainment, some soldiers would bet on the sex of an unborn baby and then slice open a woman's womb to determine the winner.

The RUF was notorious for amputating the limbs of those victims it did not murder, particularly children. Brandishing machetes, RUF troops amputated the hands, arms, and legs of tens of thousands of Sierra Leoneans. The RUF indicated that the reason for these actions was that amputees could no longer grow rice, which might be used to support government troops, nor could they vote. The RUF is also said to have practised cannibalism.

The RUF was created by Sankoh and two allies, Abu Kanu and Rashid Mansaray, with substantial assistance from Charles Taylor of Liberia. At first, the RUF was popular with Sierra Leoneans, many of whom resented a Freetown elite seen as corrupt and looked forward to promised free education and health care and equitable sharing of diamond revenues. Sankoh did not stand by these promises and used funds from diamond sales to buy arms for Taylor and himself. With the diamond mines under the control of the rebel group, the RUF became singularly focused on protecting its resource base. Sierra Leone's economy collapsed, with ordinary citizens trapped between the cruelty of RUF troops and starvation. After a coup by the Armed Forces Revolutionary Council (AFRC) in 1997, the RUF and AFRC created a joint junta to control the country before evicted from the capital by the invasion of a Nigerian-led West African force that reinstated the rule of President Ahmad Tejan Kabbah.

After a failed intervention by America and other countries to implement a peace agreement in 1999, the United Nations sent peacekeeping troops in hopes of integrating the RUF into a new national army. This intervention failed as well, and by 2000 they held 500 UN peacekeepers hostage until their release was negotiated by Taylor. The British and Guineans finally sent in a small professional force in 2001. The RUF was routed and the revolution ended. Sankoh was captured by a mob and handed to the British where he was indicted for multiple war crimes by a UN-backed court.

The RUF attempted to stand as political party in an election in 2002, but its presidential candidate, Alimamy Pallo Bangura , received just 1.7% of the vote.