Thomas Shannon is a distinguished American diplomat who served as U.S. Under Secretary of State for Political Affairs, the highest-ranking career diplomat position in the U.S. Department of State. Previously, he held the role of Assistant Secretary of State for Western Hemisphere Affairs, overseeing U.S. foreign policy in Latin America and the Caribbean.

From 2010 to 2013, Shannon served as U.S. Ambassador to Brazil, appointed by President Barack Obama in May 2009. His tenure strengthened bilateral relations between the two nations before his departure on September 6, 2013.

After retiring from the U.S. Foreign Service in 2018, Shannon transitioned to the private sector, where he currently serves as a senior advisor at Arnold & Porter, a prominent international law firm.