Ronald Ernest Paul (born August 20, 1935) is an American author, activist, physician and retired politician who served as the U.S. representative for Texas's 22nd congressional district from 1976 to 1977 and again from 1979 to 1985, as well as for Texas's 14th congressional district from 1997 to 2013. On three occasions, he sought the presidency of the United States: as the Libertarian Party nominee in 1988 and as a candidate for the Republican Party in 2008 and 2012.

A self-described constitutionalist, Paul is a critic of several of the federal government's policies, especially the existence of the Federal Reserve and tax policy, as well as the military–industrial complex, the war on drugs, and the war on terror. He has also been a vocal critic of mass surveillance policies such as the USA PATRIOT Act and the NSA surveillance programs. In 1976, Paul formed the Foundation for Rational Economics and Education (FREE), and in 1985 was named the first chairman of the conservative PAC Citizens for a Sound Economy, both free-market groups focused on limited government. He has been characterized as the "intellectual godfather" of the Tea Party movement, a fiscally conservative political movement started in 2007 and popularized in 2009 that is largely against most matters of interventionism.