John Luman Smith (born June 5, 1969) is an American attorney who has served in the United States Department of Justice as an assistant U.S. attorney, acting U.S. attorney, and head of the department's Public Integrity Section. He was also the chief prosecutor at the Kosovo Specialist Chambers, an international tribunal at The Hague tasked with investigating and prosecuting war crimes in the Kosovo War. He served as a Special Counsel for the Department of Justice from November 18, 2022 until his resignation on January 10, 2025.

In November 2022, attorney general Merrick Garland appointed Smith an independent special counsel, responsible for overseeing two preexisting Justice Department criminal investigations into former president Donald Trump, three days after Trump announced his 2024 presidential campaign: one regarding Trump's role in the January 6 U.S. Capitol attack, and the other into alleged mishandling of government records, including classified documents. The documents case resulted in a 37-count indictment of Trump in June 2023 to which three counts were later added in July. In August, the January 6 case resulted in an indictment on four charges.

The classified documents case was dismissed by judge Aileen Cannon in July 2024, on the grounds that Smith was unlawfully appointed as special counsel. Smith's office initially appealed the ruling, but ultimately abandoned the appeal after Trump won the 2024 US presidential election. The election subversion case was dismissed by judge Tanya Chutkan in November 2024, on the grounds that the Office of Legal Counsel held that Trump as President-elect could not be charged consistent with the Constitution.

After Trump gained the presidency again, the Office of Special Counsel opened an investigation into Smith, which it announced on August 1, 2025, alleging that his investigations into Trump's actions had been politically motivated.

Smith was born on June 5, 1969. He grew up in Clay, New York, a suburb of Syracuse. His father was a draftsman of air-conditioning systems; his mother was a homemaker for most of Smith's childhood. He graduated from Liverpool High School in 1987, where he played football and baseball. He then studied political science at the State University of New York at Oneonta, graduating in 1991 with a Bachelor of Arts, summa cum laude. Smith then attended Harvard Law School, from which he graduated in 1994 with a Juris Doctor, cum laude.

After graduating from law school, Smith joined the Manhattan District Attorney's office, serving as assistant district attorney. He was a member of the sex crimes and domestic violence units of the DA's office. He joined the United States Attorney's Office for the Eastern District of New York in 1999. As an assistant U.S. attorney at the Brooklyn-based office, he prosecuted the police officers who brutalized and sexually assaulted Abner Louima, and led the case towards the death penalty—which was later overturned—against Ronell Wilson, who murdered two members of the New York Police Department. On one occasion he reportedly slept in an apartment building hallway for an entire weekend so he could intercept a witness in a domestic violence case and convince her to testify.

From 2008 to 2010, Smith worked as investigation coordinator for the Office of the Prosecutor of the International Criminal Court in The Hague, Netherlands. In that position, he oversaw cases against government officials and militia members accused of war crimes and genocide. In 2010, Smith returned to the U.S. to become chief of the U.S. Department of Justice's Public Integrity Section (PIN). Among his first responsibilities was evaluating current investigations, and he recommended closing investigations into several members of Congress. He spent five years as chief of PIN, where he prosecuted a variety of corruption cases, including those against Virginia governor Bob McDonnell, U.S. representative Rick Renzi, Jeffrey Sterling, a Central Intelligence Agency officer who shared national secrets, New York State Assembly speaker Sheldon Silver, and North Carolina Senator John Edwards. McDonnell, Renzi, Sterling, and Silver were found guilty, though the Supreme Court later unanimously overturned McDonnell's conviction. Edwards' case ended in a mistrial.

In 2015, Smith became an assistant U.S. attorney in the Middle District of Tennessee, at Nashville. He became the acting U.S. attorney in March 2017 upon the resignation of David Rivera, and resigned effective September 2017 after the nomination of Donald Q. Cochran. Smith became the vice president and head of litigation for Hospital Corporation of America in 2017.