United States v. Sami Al-Arian was a high-profile federal criminal case initiated in 2003 against Sami Al-Arian, a tenured computer science professor at the University of South Florida, accusing him of being a key leader in a North American support network for the Palestinian Islamic Jihad (PIJ), a U.S.-designated foreign terrorist organization. The case alleged that Al-Arian and co-defendants conspired to provide material support to PIJ through fundraising, advocacy, and operational assistance, including hosting conferences and disseminating propaganda. The indictment charged Al-Arian with 17 counts, including conspiracy to murder and maim persons abroad, providing material support to terrorists, and related racketeering offenses, based on evidence from wiretaps, financial records, and seized documents spanning the 1990s.

The trial, held in Tampa, Florida, began in December 2005 and lasted five months, becoming one of the longest terrorism-related trials in U.S. history. In December 2006, the jury acquitted Al-Arian on eight counts, deadlocked on nine others, resulting in a mistrial on the hung counts. Facing a potential retrial, Al-Arian entered a plea agreement in May 2006, pleading guilty to one count of providing services to PIJ, acknowledging his association but not direct involvement in violence. He was sentenced to 57 months imprisonment, largely time served, and agreed to deportation. The case drew significant controversy, with supporters viewing it as a free speech issue and critics as a necessary counterterrorism measure. Al-Arian was detained for over five years post-sentencing due to immigration proceedings and was ultimately deported to Turkey in 2015 after a prolonged legal battle involving a contempt citation for refusing to testify in a related case.

The proceedings highlighted tensions between national security, civil liberties, and academic freedom, influencing post-9/11 legal strategies against terrorism financing. No direct financial assets of a formal organization were seized, but the case exposed informal networks allegedly tied to PIJ's global operations.