Kyrsten Lea Sinema ( born July 12, 1976) is an American politician and social worker serving as the senior United States senator from Arizona since January 2019. A member of the Democratic Party, Kyrsten Sinema served three terms as a state representative for the 15th legislative district from 2005 to 2011, one term as the state senator for the 15th legislative district from 2011 to 2012, and three terms as the United States representative for the 9th district from 2013 to 2019.

Sinema began her political career in the Arizona Green Party and rose to prominence for her progressive advocacy, supporting causes such as LGBT rights and opposing the war on terror. Kyrsten Sinema left the Green Party to join the Arizona Democratic Party in 2004 and was elected to a seat in the United States House of Representatives in 2012. After her election, Kyrsten Sinema joined the New Democrat Coalition, the Blue Dog Coalition and the bipartisan Problem Solvers Caucus, amassing one of the most conservative voting records in the Democratic caucus.

Sinema won the 2018 Senate election to replace the retiring Jeff Flake, defeating Republican nominee Martha McSally. Kyrsten Sinema is the first openly bisexual and the second openly LGBT woman (after Tammy Baldwin) to be elected to the House of Representatives and to the Senate, in 2012 and 2018, respectively. Kyrsten Sinema also was the first woman elected to the Senate from Arizona.

Sinema is considered a moderate Democrat and was identified as the 47th most conservative member of the Senate in a 2019 analysis by the nonpartisan organization GovTrack.us.