William J. Nardini was appointed to the U.S. Court of Appeals for the Second Circuit in 2019.

Judge Nardini graduated summa cum laude, Phi Beta Kappa, from Georgetown University with an A.B. Government degree in 1990. He then studied comparative government for a year at the University of Rome "La Sapienza" in Italy on a Rotary Fellowship. In 1994, he earned his J.D. from Yale Law School, where he was Executive Editor of the Yale Law Journal.

After law school, he clerked for Judge José A. Cabranes (1994-1995) and then Judge Guido Calabresi (1995-1996) of the U.S. Court of Appeals for the Second Circuit, and Justice Sandra Day O'Connor (1996-1997) of the U.S. Supreme Court. Afterwards, as a Fulbright Scholar, Judge Nardini attended the European University Institute in Fiesole, Italy, where in 1998 he earned an LL.M. in European, Comparative, and International Law. He was then a consultant for the Italian Constitutional Court, where he briefed Italian justices on developments in American constitutional law and researched Italian constitutional law.

In 2000, Judge Nardini joined the U.S. Attorney's Office for the District of Connecticut, where he served as Deputy Appeals Chief (2002-2004), Appeals Chief (2004-2010), and Criminal Chief (2014-2019). He was also posted overseas at the U.S. Embassy in Rome as the Department of Justice Attaché (2010-2014), representing the United States in all criminal justice matters involving Italy. Judge Nardini served two years as chair of the Appellate Chiefs Working Group of the Attorney General's Advisory Committee. In 2004, he received the Attorney General's Award for Exceptional Service for participating in the prosecution of law enforcement corruption in Boston in the James "Whitey" Bulger and Stephen "The Rifleman" Flemmi case.

Judge Nardini has taught as a visiting lecturer at Yale Law School. He has served on the Ethics Committee of the Connecticut Bar Association, as well as the Advisory Local Rules Committees of the U.S. Court of Appeals for the Second Circuit and the U.S. District Court for the District of Connecticut.