Charles Ernest Grassley (born September 17, 1933) is an American politician serving as the president pro tempore of the United States Senate since 2025, a role he also held from 2019 to 2021. A member of the Republican Party, Grassley is the senior United States senator from Iowa, serving since 1981.

He is the dean of the United States Senate. Before becoming a senator, Grassley served eight terms in the Iowa House of Representatives (1959–1975) and three terms in the United States House of Representatives (1975–1981). He has served three stints as Senate Finance Committee chairman during periods of Republican Senate majority.