Mark Henry Gitenstein (born March 7, 1947) is an American lawyer and diplomat who is serving as the United States ambassador to the European Union since 2022. He was nominated by President Joe Biden on July 27, 2021, and confirmed by the United States Senate on December 18, 2021. He formerly served as the United States ambassador to Romania from 2009 to 2012; he was nominated by President Barack Obama on June 11, 2009 and confirmed by the Senate on July 8, 2009.