The New Economic Policy, or NEP () was a system of economic reforms, partly market-oriented, that Vladimir Lenin instituted in the Russian SFSR and then Soviet Union. The emergency policy of War communism, introduced during the Russian Civil War, was terminated, and the NEP replaced it in 1921 as a recovery measure.

The NEP restored some private ownership to small parts of the economy, especially farming. It replaced the policy of "War Communism", which had been used during the Russian civil war and which was deemed unsustainable in an underdeveloped country like Russia, with a kind of "Market Socialism", whereby nationalised (government owned) industries were allowed to operate autonomously, while a market system was introduced in agriculture. To explain the NEP, Lenin had said "We are not civilized enough for socialism", referring to the fact that Russia was still a primarily agrarian nation, with a very small urban population and a weak industrial base, and thus it did not meet the economic criteria necessary for full socialism.

NEP succeeded in creating an economic recovery after the devastating effects of the First World War, the Russian revolution and the Russian civil war. Most notably, it increased agricultural production enormously and ended the ongoing famine. It was abandoned a few years after Lenin's death in 1924, since it was deemed that the original objectives of the NEP had been achieved and it was time to move on. The NEP was generally believed to be intended as an interim measure, and proved highly unpopular with the strong Marxists in the Bolshevik party because of its compromise with some capitalistic elements. They saw the NEP as a betrayal of communist principles, and they believed it would have a negative long-term economic effect, so they wanted a fully planned economy instead. On the other hand, Lenin has been quoted as saying: "NEP is for serious (real) and for a long time." Sometimes this has been used to claim that if only Lenin were to stay alive longer, NEP would have continued beyond 1929, and the controversial collectivization would have never happened, or it would have been carried out differently. Such claims are debatable.

Lenin's successor, Stalin, eventually introduced full central planning (although this had originally been the idea of the Left Opposition, which Stalin purged from the Party), re-nationalised the whole economy, and from the late 1920s onwards introduced a policy of rapid industrialization. Stalin's collectivization of agriculture has been his most notable, and most destructive departure from the NEP approach. It is often argued that industrialization could have been achieved without any collectivization just by taxing the peasants more, much like it has happened in Meiji Japan, Bismarck's Germany, and in post-war South Korea and Taiwan. It is also argued, however, that such an industrialization would have taken much longer than Stalin's ultra-rapid version, leaving the Soviet Union far behind Western countries like Germany in terms of industrial and military output, thus possibly resulting in a victory for Nazi Germany in World War II.