Romanism is a derogatory term for Roman Catholicism used when anti-Catholicism was more common in the United States.

The term was frequently used in late-nineteenth and early-twentieth century Republican invectives against the Democrats, as part of the slogan "Rum, Romanism, and Rebellion" (referencing the Democratic party's constituency of Southerners and anti-Temperance, frequently Catholic, working-class immigrants). The term and slogan gained particular prominence in the 1884 presidential campaign and again in 1928, in which the Democratic candidate was the outspokenly anti-Prohibition Catholic Governor of New York Al Smith.

The term was also used by Democratic Unionist Party founder Ian Paisley in anti-Catholic speeches