Thad William Allen (born 16 January 1949) is a former admiral of the United States Coast Guard who served as the 23rd commandant from 2006 to 2010.

He officially retired from the U.S. Coast Guard on 30 June 2010, but continued to serve as National Incident Commander for an additional three months.

He attended the United States Coast Guard Academy in New London, Connecticut, where he was a standout football player, graduating in 1971.

[7] In his four decades of service, Allen has held operational command both at sea and ashore, conducting missions to support the maritime safety, security and environmental stewardship interests of the nation.

[2] On 9 September 2005, Allen was given full command of the Bush administration's Hurricane Katrina onsite relief efforts.

[13] On 30 April 2010, Homeland Security Secretary Janet Napolitano announced that Allen would serve as the National Incident Commander for the federal government's response to the Deepwater Horizon oil spill in the Gulf of Mexico.

On 25 July 2024, the House Committee on Oversight and Accountability investigating the Coast Guard’s mishandling of serious misconduct, including racism, hazing, discrimination, sexual harassment, sexual assault, and the failure to disclose internal investigations into those issues to Congress requested that Admiral Allen participate in a voluntary transcribed interview.

Additionally, as the Chief of Staff during and the Commandant following the date range investigated by OFA, the Committee is interested in learning more about what efforts were made to notify Congress or conceal misconduct.

[18] On 28 November 2011, Booz Allen Hamilton named Allen a Senior Vice President, joining the firm's Justice and Homeland Security business and leading development of thought leadership and client engagement regarding the direction of law enforcement and homeland security.

[22] His official U.S. Coast Guard portrait, painted by artist Michele Rushworth was unveiled at Fort Lesley J. McNair upon his retirement.