John Hennessey-Niland is an American diplomat who had served as the United States ambassador to Palau from 2020 to 2022.

Other diplomatic assignments include Deputy Chief of Mission and later Chargé d’Affaires at the Embassy of the United States, Dublin, Ireland; Director at the National Security Council for the G-20/G-7; and Director of International Narcotics and Law Enforcement at the Embassy of the United States, Islamabad, Pakistan.

[1] On September 30, 2019, President Donald Trump nominated Hennessey-Niland to be the next United States ambassador to Palau.

[5][6] After retiring from his role as Ambassador, Hennessey-Niland joined the faculty at the Bush School of Government and Public Service at Texas A&M University as a Professor of Practice.

[1] Hennessey-Niland has received the Department of State Foreign Policy Advisors of the Year Award and the Navy Meritorious Civilian Service Medal.