Elbridge Colby

Elbridge Colby
Official portrait, 2025
Under Secretary of Defense for Policy
Assumed office
April 9, 2025
PresidentDonald Trump
Preceded byColin Kahl
Deputy Assistant Secretary of Defense
For Strategy and Force Development
In office
May 2017 – June 2018
PresidentDonald Trump
Preceded byPosition established
Succeeded byPosition abolished
Personal details
BornElbridge Andrew Colby
(1979-12-30) December 30, 1979
PartyRepublican
RelativesWilliam Colby (grandfather)
EducationHarvard University (AB)
Yale University (JD)

Elbridge Andrew Colby (born December 30, 1979) is an American national security policy professional who is the under secretary of defense for policy since April 9, 2025. He previously served as deputy assistant secretary of defense for strategy and force development from 2017 to 2018 during the first Trump administration. He played a key role in the development of the 2018 U.S. National Defense Strategy, which, among other things, shifted the U.S. Defense Department's focus to China. He is the grandson of former CIA director William Colby.

In June 2018, Colby was appointed as director of the Defense Program at the Center for a New American Security (CNAS). In 2019, he co-founded the Marathon Initiative, a grand strategy think tank, with Wess Mitchell. In December 2024, President-elect Donald Trump nominated Colby to serve as the under secretary of defense for policy in the second Trump administration.

Identifying as a realist, Colby believes China is the principal threat faced by the United States. He believes the US should shift its military resources to Asia to prevent a Chinese takeover of Taiwan. Colby supports reducing military aid to Ukraine. During the AUKUS review in 2025, Colby pressured Australia to confirm what role it would play in a war with China over Taiwan.