Nathan Castellano is Counsel at the global law firm, Freshfields. He focuses his practice on U.S. government contracts and grants, advising clients on litigation, investigations, compliance counseling, negotiation, and complex transactions. He brings deep experience navigating the intersection of public procurement and private enterprise, and is widely recognized for his thought leadership in the field.
Before joining Freshfields, Nathan held senior roles at two leading international law firms, where he built and led teams handling high-stakes disputes, internal investigations, transactions, and strategic regulatory matters for federal contractors and grantees.
Nathan clerked for the Hon. Jimmie V. Reyna of the U.S. Court of Appeals for the Federal Circuit and previously served in an advisory role at the World Bank.
He is a a co-author of the classic text "Formation of Government Contracts" (5th Edition), and he is a Contributing Author to The Nash & Cibinic Report. Nathan’s publications are cited in judicial opinions, administrative decisions, and leading treatises. He has been recognized by Chambers USA as “Up and Coming” in Government Contracts (2025), Law360 Rising Stars (2023), and Best Lawyers: Ones to Watch (2021–2025).