The term Blaine Amendment refers to amendments or provisions that exist in most state constitutions in the United States that forbid direct government aid to educational institutions that have any religous affiliation.

The amendments are named after James G. Blaine (1830-1893), a former Speaker of the United States House of Representatives, who led a campaign to have the provision added to the United States Constitution. In 1875, the proposed amendment passed by a vote of 180 to 7 in the House of Representatives, but failed to achieve the necessary two-thirds majority by four votes in the United States Senate.

Supporters of the amendment then turned their attention to state legislatures, where their efforts were met with far greater success: Eventually, all but 11 states (Arkansas, Connecticut, Louisiana, Maine, Maryland, New Jersey, North Carolina, Rhode Island, Tennessee, Vermont, and West Virginia) passed laws that meet the general criteria for designation as "Blaine Amendments," in that they ban the use of public funds to support sectarian private schools (in many cases, the laws were included in constitutions drafted by newly-formed states concomitant with their admission to the Union and are thus technically not "amendments" in the strictest sense).

While efforts were made from time to time to repeal the amendments in some states (such as an unsuccessful attempt to do so in New York State in the mid-1960s, which probably failed at least in part because it entailed the adoption of an entirely new state constitution rather than the repeal of the Blaine amendment to the existing ones), the amendments attracted little real attention until the 1990s, when repeal campaigns became more frequent. Most of the recent repeal bids have been led by fundamentalist or evangelical Protestants — an irony of sorts since it was members of these same denominations who had actually spearheaded the drive to pass the amendments originally, fearing the rising prominence of the Roman Catholic Church in the American educational apparatus. The modern movement to strike down the Blaine Amendments is linked to the advocacy of school voucher programs, as the amendments clearly prohibit the latter with regard to religiously-based or affiliated private schools, which constitute by far the bulk of such institutions in the United States.