The Palmer Raids were a series of raids conducted in November 1919 and January 1920 by the United States Department of Justice under the administration of President Woodrow Wilson to capture and arrest suspected socialists, especially anarchists and communists, and deport them from the United States. The raids particularly targeted Italian immigrants and Eastern European Jewish immigrants with alleged leftist ties, with particular focus on Italian anarchists and immigrant leftist labor activists. The raids and arrests occurred under the leadership of Attorney General A. Mitchell Palmer, with 3,000 arrested. Though 556 foreign citizens were deported, including a number of prominent leftist leaders, Palmer's efforts were largely frustrated by officials at the U.S. Department of Labor, which had authority for deportations and objected to Palmer's methods.

The Palmer Raids occurred in the larger context of the First Red Scare, a period of fear of and reaction against communists in the U.S. in the years immediately following World War I and the Russian Revolution. There were strikes that garnered national attention, and prompted race riots in more than 30 cities, as well as two sets of bombings in April and June 1919, including one bomb mailed to Palmer's home.