Jacob Jeremiah Sullivan (born November 28, 1976) is an American attorney who served as the U.S. national security advisor from 2021 to 2025 under President Joe Biden.

Sullivan previously served as Director of Policy to President Barack Obama, National Security Advisor to then-Vice President Biden and Deputy Chief of Staff to Secretary Hillary Clinton at the U.S. Department of State. Sullivan also served as senior advisor to the U.S. federal government at the Iran nuclear negotiations and senior policy advisor to Clinton's 2016 presidential campaign, as well as visiting professor at Yale Law School.

On November 23, 2020, President-elect Biden announced that Sullivan would be appointed the National Security Advisor. He took office on January 20, 2021.

Sullivan was born in Burlington, Vermont, to a family of Irish descent and grew up in Minneapolis, Minnesota. His father worked for the Star Tribune and was a professor at the University of Minnesota School of Journalism and Mass Communication, and his mother was a high school guidance counselor. Sullivan attended Southwest High School in Minneapolis, where he graduated in 1994. He was a Coca-Cola Scholar, debate champion, president of the student council, and voted "most likely to succeed" in his class.

Educated in the United States and United Kingdom, Sullivan first attended Yale University, where he majored in international studies and political science and was awarded the Alpheus Henry Snow Prize. He was inducted into Phi Beta Kappa his senior year and graduated summa cum laude with distinction in 1998 with a Bachelor of Arts. Sullivan won a Rhodes Scholarship to attend Magdalen College, Oxford, where he studied international relations. He was also awarded a Marshall Scholarship, which he declined in favor of the Rhodes. While at Oxford, Sullivan served as a managing editor of the Oxford International Review. He graduated with a Master of Philosophy. He graduated with a Juris Doctor from Yale Law School in 2003. He is a member, and former board member, of the Truman National Security Project.

At Yale, he was an editor of the Yale Law Journal, the Yale Law & Policy Review, and the Yale Daily News. He interned at the Council on Foreign Relations, was a member of the Yale Debate Association, and earned a Truman Scholarship in his junior year. He also worked for Brookings Institution president Strobe Talbott at the Yale Center for the Study of Globalization.

After graduating from law school, Sullivan clerked for Judge Guido Calabresi of the United States Court of Appeals for the Second Circuit and then for Associate Justice Stephen Breyer of the United States Supreme Court. After his clerkships, Sullivan returned to his hometown of Minneapolis to practice law at Faegre & Benson and taught law as an adjunct professor at the University of St. Thomas School of Law. After Faegre & Benson, Sullivan worked as chief counsel to Minnesota senator Amy Klobuchar, who connected him to Hillary Clinton.

In 2008, Sullivan was an advisor to Hillary Clinton during the primary cycle and then to Barack Obama during the general election campaign. He prepared Clinton and Obama for debates. When Clinton became secretary of state, Sullivan was named her deputy chief of staff and Director of Policy Planning, and traveled with her to 112 countries. In 2012, Sullivan approvingly wrote that Al-Qaeda "was on our side in Syria" to Clinton. Clinton later joked that Sullivan was a potential future president of the United States.