Dianne Emiel Feinstein (née Goldman; June 22, 1933 – September 29, 2023) was an American politician who served as a United States senator from California from 1992 until her death in 2023. A member of the Democratic Party, she previously served as the 38th mayor of San Francisco from 1978 to 1988.

A San Francisco native, Feinstein graduated from Stanford University in 1955. She was elected to the San Francisco Board of Supervisors in 1969 and immediately became the board's first female president upon her appointment in 1970. In 1978, during a third stint as the board's president, the assassinations of Mayor George Moscone and City Supervisor Harvey Milk drew national attention. Feinstein succeeded Moscone as mayor and became the first woman to serve in that position. During her tenure, she led the renovation of the city's cable car system and oversaw the 1984 Democratic National Convention. Despite a recall attempt in 1983, Feinstein was a popular mayor and was named the most effective mayor in the country by City & State in 1987.

After losing a race for governor in 1990, Feinstein was elected to the U.S. Senate in a 1992 special election. In November 1992, she became California's first female U.S. senator; shortly afterward, she became the state's senior senator when Alan Cranston retired in January 1993. Feinstein was reelected five times. In the 2012 election, she received 7.86 million votes, which was, until 2024, the most popular votes received by any U.S. Senate candidate in history.

As a senator, Feinstein authored the 1994 Federal Assault Weapons Ban, was the first woman to chair the Senate Rules Committee and the Senate Intelligence Committee, and was the first woman to preside over a U.S. presidential inauguration. She chaired the Senate Intelligence Committee from 2009 to 2015 and was the ranking member of the Senate Judiciary Committee from 2017 to 2021.

Feinstein's last years in office were marred by poor health and concerns about her mental acuity. In February 2023, Feinstein announced she would not seek reelection in 2024. Seven months later, she died in office at the age of 90. By the time of her death, Feinstein was the oldest sitting U.S. senator and member of Congress. She was also the longest-serving U.S. senator from California and the longest-tenured female senator in history.

Feinstein was born Dianne Emiel Goldman on June 22, 1933, in San Francisco to Leon Goldman, a prominent surgeon, and his wife, Betty (née Rosenburg), a former model. Her paternal grandparents were Jewish immigrants from Poland. Her maternal grandparents, the Rosenburgs, were from Saint Petersburg, Russia. Although they were of German-Jewish ancestry, they practiced the Russian Orthodox (Christian) faith, as was required of Jews in Saint Petersburg. Christianity was passed down to Feinstein's mother, who insisted on her transfer from a Jewish day school to a prestigious local Catholic school, but Feinstein listed her religion as Judaism.

She graduated from Convent of the Sacred Heart High School in 1951 and from Stanford University in 1955 with a Bachelor of Arts in history. Feinstein's mother was abusive, prone to alcohol-fueled outbursts and, according to Feinstein's sister Yvonne Banks, emotionally unpredictable. Later, Feinstein's mother received a brain scan that found that the part of her brain responsible for judgment had atrophied, "possibly because of complications from a severe illness as a child".

Feinstein reportedly identified as half-Russian.