Marc Ostfield is an American academic and diplomat who had served as United States ambassador to Paraguay.

Ostfield earned a Bachelor of Arts in women's studies, a Master of Science in human sexuality education, and a Doctor of Philosophy in communication from the University of Pennsylvania.

From 2009 to 2013, he served as director of the Office of Policy and Global Issues in the Bureau of European and Eurasian Affairs.

[2] On June 15, 2021, President Joe Biden nominated Ostfield to be the next United States ambassador to Paraguay.

[7] The government of Paraguay on August 8, 2024 effectively requested Ostfield to leave in response to the US imposing sanctions against the cigarette manufacturer Tabacalera del Este and four other firms for supporting the illicit enrichment of former president Horacio Cartes.