Alan Mark Grayson (born March 13, 1958) is an American politician who served as the U.S. representative for Florida's 8th congressional district from 2009 to 2011 and Florida's 9th congressional district from 2013 to 2017. A member of the Democratic Party, he was defeated for reelection in 2010 by Republican Daniel Webster; he was then reelected in 2012 for a second, non-consecutive term in the U.S. House of Representatives in another district, defeating Republican Todd Long.

In 2016, Grayson decided not to run for reelection to his House seat in order to run for the U.S. Senate. He was defeated 59–18% in the Democratic primary by fellow Representative Patrick Murphy, who went on to lose the general election to incumbent Republican Marco Rubio. In 2018, Grayson entered the race for the 9th congressional district. He was defeated in the Democratic primary by his successor Darren Soto, 66–34%. On March 27, 2021, Grayson announced his candidacy for the 2022 U.S. Senate election in Florida to challenge Rubio. On June 14, 2022, Grayson announced that he would drop his bid for Senate and instead run in the open race for Florida's 10th congressional district, in which he lost the Democratic primary. In 2024, he unsuccessfully ran for the Florida Senate, finishing third in the primary. Grayson ran in the 2025 Florida Senate special election and is currently running in the 2026 United States Senate special election in Florida.

Grayson was born in the Bronx, New York City, New York, to Dorothy Ann (née Sabin) and Daniel Franklin Grayson. He grew up in Adee Towers, a building financed by the Mitchell–Lama Housing Program, and graduated from the Bronx High School of Science in 1975. Grayson worked his way through Harvard College as a janitor and nightwatchman, and also features reporter for Boston Phoenix. He graduated magna cum laude and Phi Beta Kappa with a Bachelor of Arts degree with a Special Concentration in Urban Studies in 1978. After working two years as an economist, he returned to Harvard for graduate studies. In 1983, he earned a J.D. cum laude from Harvard Law School and a M.P.P. from the John F. Kennedy School of Government. He also completed all coursework and the comprehensive examination for a Ph.D. in government.

Grayson wrote his master's thesis on gerontology. In 1986, he helped found the non-profit Alliance for Aging Research in Washington, D.C., and served as an officer of the organization for more than twenty years.

Grayson worked as a law clerk at the Colorado Supreme Court in 1983, and at the U.S. Court of Appeals for the D.C. Circuit from 1984 to 1985, where he worked with two judges who later joined the U.S. Supreme Court: Ruth Bader Ginsburg and Antonin Scalia. He was an associate in the Washington, D.C., office of the law firm Fried, Frank, Harris, Shriver & Jacobson for five years, where he specialized in contract law.

In 1991 he founded the law firm Grayson & Kubli, which concentrated on government contract law. He was a lecturer at the George Washington University government contracts program and a frequent speaker on the topic. In the 2000s, he worked as a plaintiffs' attorney specializing in whistleblower fraud cases aimed at Iraq War contractors. One contractor, Custer Battles, employed individuals who were found guilty of making fraudulent statements and submitting fraudulent invoices on two contracts the company had with the Coalition Provisional Authority in Iraq. On behalf of his clients, Grayson filed suit under the False Claims Act and its qui tam provisions. The jury verdict was more than $13 million, which was upheld on appeal in April 2009. The Iraq War contractor fraud case brought Grayson his first national attention. In 2006, a reporter for The Wall Street Journal described Grayson as "waging a one-man war against contractor fraud in Iraq" and as a "fierce critic of the war in Iraq" whose car displayed bumper stickers such as "Bush lied, people died."

Grayson made his fortune as the co-founder and first president of IDT Corporation (International Discount Telecom).

In 2006, Grayson first entered into electoral politics, losing the 2006 Democratic primary for Florida's 8th congressional district to Charlie Stuart, a prominent local businessman and conservative Democrat. Stuart went on to lose the general election to incumbent Republican Ric Keller.