Stephen Clark Bullock (born April 11, 1966) is an American politician and lawyer who served as the 24th governor of Montana from 2013 to 2021. He is a member of the Democratic Party.

Born in Missoula, Montana, Bullock graduated from Claremont McKenna College and Columbia Law School. He began his career working as legal counsel to the Secretary of State of Montana before becoming the Executive Assistant Attorney General and acting Chief Deputy Attorney General of Montana. Bullock then entered private practice as a lawyer for Steptoe & Johnson. He was an adjunct professor at George Washington University Law School before opening his own law firm upon returning to Montana. In 2008, Bullock was elected Attorney General of Montana, and he served one term from 2009 to 2013.

Bullock declared his candidacy for governor of Montana on September 7, 2011. Bullock won the Democratic primary with 87% of the vote and defeated Republican former Congressman Rick Hill in the general election with 48.9% of the vote. In 2016, Bullock was reelected with 50.3% of the vote, defeating Republican nominee Greg Gianforte.

Bullock chaired the National Governors Association from 2018 to 2019. He was a Democratic candidate for President of the United States in 2020. After suspending his presidential campaign, he announced his candidacy for the United States Senate in the 2020 election. Bullock lost the 2020 Senate election to incumbent Senator Steve Daines.

On January 20, 2022, Bullock was appointed by Secretary of the Interior Deb Haaland to the inaugural board of directors of the Foundation for America's Public Lands. Bullock's post-gubernatorial public appearances have tended to focus on the importance of bipartisanship, moderation, and democracy. As of 2024, he is the most recent Democrat to serve as both Attorney General, and Governor of Montana.