Catherine Marie Cortez Masto (born March 29, 1964) is an American lawyer and politician serving as the senior United States senator from Nevada, a seat she has held since 2017. A member of the Democratic Party, Cortez Masto served as the 32nd attorney general of Nevada from 2007 to 2015.

Cortez Masto graduated from University of Nevada, Reno and Gonzaga University School of Law. She worked four years as a civil attorney in Las Vegas and two years as a criminal prosecutor for the U.S. Attorney's Office in Washington, D.C. before being elected Nevada attorney general in 2006, replacing George Chanos. Reelected in 2010, she was not eligible to run for a third term in 2014 because of lifetime term limits established by the Constitution of Nevada.

Cortez Masto narrowly defeated Republican Joe Heck in the 2016 United States Senate election in Nevada to replace outgoing Democratic senator Harry Reid, becoming the first woman elected to represent Nevada in the Senate and the first Latina elected to serve in the upper chamber. She took office on January 3, 2017, and became Nevada's senior senator in January 2019, when Dean Heller left the Senate following his defeat. She was narrowly reelected in 2022, defeating Republican nominee Adam Laxalt.