Purge, in Communist Party political slang, is an abbreviation of the expression purge of the Party ranks.

The first major Communist Party purge in the Soviet Union was performed as early as in 1921. About 220,000 members were purged or left party at this time. The purge was justified by the nessessity to get rid of the members that joined the Party simply to be on the winning side. The major criteria were social origins (members of working classes were normally accepted without question) and contributions to the revolutionary cause.

The first purge of the Stalin era was performed in 1929–1930 according to the resolution of the XVI Party Conference. Over 10% of the Party members were purged. At the same time a significant number of new members, industrial workers, joined the Party.

The next systematic Party purge in the Soviet Union was declared in December 1932 to be performed turing 1933. This time on the period of purge new memberships were temporarily suspended. A joint resolution of the Party Central Committee and Central Revision Committee specified the criteria for purge and called for setting special Purge Commissions, to which every communist had to report. Also, this purge concerned members of the Central Committee, Central Revision Committee, which previously were immune to purges, because they were elected at Party Congresses. In particular, Bukharin, Rykov, and Tomsky had to try hard to defend themselves during this purge. At this time, of 1.9 mln members, about 18% were purged.

In itself, the term was innocent enough: within 1921–1933 in the Soviet Union, for example, some 800,000 people were purged or left the Party, but suffered no worse fate.

But from 1936 onwards, during the Great Purge, the term changed its meaning, because being expelled from the Party came to mean almost certain arrest, imprisonment or even execution.

Following Stalin's death, purges as systematic campaigns of expulsion from the Party stopped and loss of the Party membership meant only loss of possible nomenklatura privileges.