Susan Bysiewicz (/ˈbaɪzəwɪts/ BYE-zə-wits; born September 29, 1961) is an American politician and attorney who has served as the 109th lieutenant governor of Connecticut since 2019. She previously served as the 72nd secretary of the state of Connecticut from 1999 to 2011 and a member of the Connecticut House of Representatives from 1993 to 1999.

She was briefly a candidate for governor of Connecticut in 2010, before dropping out to run for Connecticut Attorney General. She was disqualified from running for the office by the Connecticut Supreme Court and announced in 2011 that she was running for the United States Senate in the 2012 election to replace the retiring Joe Lieberman but lost the Democratic primary to U.S. Representative Chris Murphy, who went on to win the general election.

In 2018, Bysiewicz filed papers to run for governor of Connecticut but withdrew shortly before the Democratic Convention, in order to run for lieutenant governor as Ned Lamont's running mate. She was nominated for lieutenant governor during the state primary.

Bysiewicz was born September 29, 1961, in New Haven and raised on a farm. The daughter of Stan and Shirley Bysiewicz, she was raised by a Catholic family of Polish and Greek descent in Middletown, Connecticut. She received her Bachelor of Arts from Yale University and her Juris Doctor from Duke University School of Law. During law school, she wrote Ella: A Biography of Governor Ella Grasso. Bysiewicz practiced law in New York City for two years as an associate of White & Case (1986–88). In 1988 she became associated with the Hartford firm of Robinson & Cole, L.L.C. where she practiced for four years, and then joined the legal department of Aetna where she was employed from 1992 to 1994.

After the redistricting that followed the 1990 Federal Census, she decided to run in the newly redrawn Connecticut's 100th Assembly District, and defeated Republican Joseph Milardo by a margin of 61–39%. She was a part of the largest Freshman class of the state legislature since 1974. In 1994, she won re-election to a second term with 67% of the vote. In 1996, she won re-election to a third term with 66% of the vote.

She was elected state representative for the 100th Assembly District of Connecticut for three successive terms starting in 1992, representing until 1998 about 22,000 constituents living in parts of the towns of Middletown (64% of her constituents) and Middlefield (10%), and throughout the town of Durham (26%).

In the House, she investigated the political power of County Sheriffs and Connecticut's last vestige of patronage politics at the local level. The sheriffs are only political positions of Connecticut county government, which was eliminated in 1960. Democrats control the Hartford County Sheriff's Department, for example, and of the 288 deputy and special deputy sheriffs working, the Program Review and Investigations Committee found just two Republicans.

In 1998, Bysiewicz sought the Democratic nomination for Secretary of the State. At the state Democratic Convention, she lost the party's endorsement for the nomination, to Representative Ellen Scalettar, but won enough delegates' votes to qualify to run for the nomination in a primary. During the primary campaign she charged her opponent opposed Megan's Law and was soft on sex offenders. She won both the nomination, and, in the general election in November, the office itself. She won re-election in 2002, but in 2005, while serving, she announced her candidacy for the Democratic nomination for the gubernatorial election of 2006. She withdrew from that race in September 2005, and on November 7, 2006, won a third term (running through 2010) as Secretary of the State.