The following are notable alumni of Georgetown Preparatory School, Maryland, United States.
- Dylan Baker, '76 - actor
- John Barrymore - Shakespearean actor and grandfather of Drew Barrymore; attended but was expelled
- Bill Bidwill, '49 - owner of NFL's Arizona Cardinals
- Brian Cashman, '85 - General Manager of New York Yankees
- Capt. Michael J. Daly, '41 - U.S. Army, retired, Medal of Honor recipient
- Rep. John Dingell, '44 - longest serving member of the U.S. House of Representatives, D.-Mich.
- Senator Christopher Dodd, '62 - U.S. Senate, D.-Conn; presidential candidate
- Hon. Neil M. Gorsuch, '85 - Judge, United States Court of Appeals for the Tenth Circuit; at the time of his confirmation, he was the youngest Court of Appeals Judge in the US; nominated to the U.S. Supreme Court by President Donald Trump
- Ian Harding, '05 - actor
- Roy Hibbert, '04 - former Georgetown University basketball player and NBA 2008 first round draft pick for the Indiana Pacers
- Hon. Thomas Hogan, '56 - chief Judge, United States District Court for the District of Columbia
- Hon. Brett Kavanaugh, '83 - former Associate Independent Counsel in the Whitewater Scandal and Staff Secretary under George W. Bush; judge on the United States Court of Appeals for the District of Columbia Circuit
- Christopher George Kennedy, '82 - son of Robert F. Kennedy; President of Merchandise Mart Properties, Inc.
- Douglas Harriman Kennedy, '86 - son of Robert F. Kennedy; Fox News Channel correspondent
- Rep. Frank LoBiondo, '64 - U.S. House of Representatives, R.-N.J.
- Marcus Mason, '03 - running back, Washington Redskins
- Dennis Murphy, '65 - Emmy Award-winning television journalist for Dateline NBC
- Kevin Plank - founder of Under Armour; attended but was expelled
- Mo Rocca (Maurice Rocca), '87 - comedian
- L. Francis Rooney, III '71 - former U.S. Ambassador to Vatican City
- Hon. Joseph E. Schmitz, '72 - former Inspector General of the Pentagon
- Anthony Paul Kennedy Shriver, '84 - co-founder of Best Buddies International; son of Eunice Kennedy Shriver and Sargent Shriver
- Mark Kennedy Shriver, '82 - former representative to the Maryland House of Delegates (15th District); son of Eunice Kennedy Shriver and Sargent Shriver
- James Whitaker, '86 - Hollywood producer and President of Production for Imagine Entertainment
- AJ Wood, '91 - former NCAA Soccer All-American and Soccer America Player of the Year; 1996 Olympian and player for MLS D.C. United and the New York/New Jersey Metrostars
- Charles Gordon Zubrod, '32 - father of modern chemotherapy