Robert Patrick Casey Jr. (born April 13, 1960) is an American lawyer and politician who served from 2007 to 2025 as a United States senator from Pennsylvania. He is a member of the Democratic Party.

Born in Scranton, Pennsylvania, Casey is the son of Bob Casey Sr., a former governor of Pennsylvania. After graduating from the College of the Holy Cross and the Catholic University of America, he practiced law in Scranton before beginning his political career as Pennsylvania Auditor General, a position he was elected to in 1996 and held until 2005.

In 2002, Casey ran for governor of Pennsylvania, but lost the Democratic primary to Ed Rendell. After being term-limited out of his position as auditor general, Casey was elected treasurer in 2004. In 2006, Casey ran for the U.S. Senate and defeated the Republican incumbent, Rick Santorum. Casey was reelected in 2012 and in 2018. In 2024, he narrowly lost reelection to Republican nominee David McCormick by a 0.22% margin.