The Johnson Amendment is a provision in the U.S. tax code, since 1954, that prohibits all 501(c)(3) non-profit organizations from endorsing or opposing political candidates. Section 501(c)(3) organizations are the most common type of nonprofit organization in the United States, ranging from charitable foundations to universities and churches. The amendment is named for then-Senator Lyndon B. Johnson of Texas, who introduced it in a preliminary draft of the law in July 1954.

In the early 21st century, some politicians, including President Donald Trump, have sought to repeal the provision, arguing that it restricts the free speech rights of churches and other religious groups. These efforts have been criticized because churches have fewer reporting requirements than other non-profit organizations, and because it would effectively make political contributions tax-deductible. On May 4, 2017, Trump signed an executive order "to defend the freedom of religion and speech" for the purpose of easing the Johnson Amendment's restrictions.

Paragraph (3) of subsection (c) within section 501 of Title 26 (Internal Revenue Code) of the U.S. Code (U.S.C.) describes organizations which may be exempt from U.S. Federal income tax. 501(c)(3) is written as follows, with the Johnson Amendment in bold letters:

(3) Corporations, and any community chest, fund, or foundation, organized and operated exclusively for religious, charitable, scientific, testing for public safety, literary, or educational purposes, or to foster national or international amateur sports competition (but only if no part of its activities involve the provision of athletic facilities or equipment), or for the prevention of cruelty to children or animals, no part of the net earnings of which inures to the benefit of any private shareholder or individual, no substantial part of the activities of which is carrying on propaganda, or otherwise attempting, to influence legislation (except as otherwise provided in subsection (h)), and which does not participate in, or intervene in (including the publishing or distributing of statements), any political campaign on behalf of (or in opposition to) any candidate for public office.[bolding added]

The amendment affects nonprofit organizations with 501(c)(3) tax exemptions, which are subject to absolute prohibitions on engaging in political activities and risk loss of tax-exempt status if violated. Specifically, they are prohibited from conducting political campaign activities to intervene in elections to public office. The Johnson Amendment applies to any 501(c)(3) organization, not just religious 501(c)(3) organizations.

The benefit of 501(c)(3) status is that, in addition to the organization itself being exempt from taxes, donors who itemize may also take a tax deduction for their contributions to the organization.

According to the Internal Revenue Service, contributions to political campaign funds, or public statements of position in favor of or in opposition to any candidate for public office, are disallowed. However, certain voter education activities (including presenting public forums and publishing voter education guides), voter registration, and get-out-the-vote drives, if conducted in a non-partisan manner, are not prohibited.

The amendment was to a bill in the 83rd Congress, H.R. 8300, which was enacted into law as the Internal Revenue Code of 1954. The amendment was proposed by Senator Lyndon B. Johnson of Texas on July 2, 1954. The amendment was agreed to without any discussion or debate and was included in Internal Revenue Code of 1954 (Aug. 16, 1954, ch. 736). The provision was considered uncontroversial at the time and continued to be included when the 1954 Code was renamed as the Internal Revenue Code of 1986 during the Ronald Reagan administration.^{[unreliable source?]}