- Braving the threat of a veto from United States President George W. Bush, U.S. Senate Republicans joined Democrats, voting
- A week after the election, which was initially too close to call, Democratic Party candidate Kyrsten Sinema is elected to the United States Senate, defeating GOP candidate Martha McSally. Sinema is the first woman elected to represent Arizona in the Senate and first Democrat to win a Senate election in the state since 1988.
- Two new Democratic senators—Doug Jones of Alabama and Tina Smith of Minnesota—are sworn in, bringing the Republican majority down to 51–49.
- Voters in Alabama go to the polls to fill the United States Senate seat vacated by current United States Attorney General Jeff Sessions. The race is between Roy Moore (R) and Doug Jones (D).
- United States senators Ben Cardin (D-MD) and Marco Rubio (R-FL) file a bill restricting arms sales to the Philippine National Police over its drug war.