Kelly Cassidy (born 1967/1968) is an American politician from Chicago. She is a Democrat and a member of the Illinois House of Representatives. She was appointed to represent the 14th district, on Chicago's North Side, in April 2011 following incumbent Harry Osterman's election to the Chicago City Council. She took office on May 16, 2011. Most notably Kelly Cassidy was the chief sponsor of House Bill 1438, making Illinois the first state to legalize the Adult-Use of Cannabis through legislature as opposed to a ballot measure.

Cassidy went to Manatee High School in Bradenton, Florida. From 1991 to 1993, she worked as the legislative director for the Chicago chapter of the National Organization for Women. From 1993 to 1997, she worked for state senate president John Cullerton, running his district office. In 1997, Cassidy joined the Cook County state's attorney's office, initially as a legislative liaison. In 2001, she became the director of programs and development for the state's attorney's office, a post she held until her appointment to the legislature in 2011. Cassidy served as a delegate to the 2012 Democratic National Convention.

Following state representative Harry Osterman's election as 48th ward alderman in February 2011, Cassidy was one of 23 candidates to seek appointment as his successor in the state house. The 14th district, which Osterman was vacating and Cassidy now represents, includes the neighborhoods of Edgewater, Andersonville, and Rogers Park. Per Illinois law, the vacancy was filled by Democratic committeemen from the wards making up the district, their votes weighted to reflect the share of the district falling in each ward. Because more than half of the 14th district's voters live in Chicago's 48th ward, that ward's committeeman – former state senator Carol Ronen – cast more than half of the votes. On April 17, the committeemen unanimously selected Cassidy to fill the vacancy.

In the 2012 Democratic primary, Cassidy was challenged by Paula Basta, a lesbian and longtime North Side activist. On March 20, 2012, Cassidy won the Democratic primary with 6,040 votes (62.4% of the vote) to Basta's 3,636 votes (37.6%).

In 2018, J. B. Pritzker appointed Cassidy to the gubernatorial transition's Restorative Justice and Safe Communities Committee.

In 2019, Cassidy was an advocate for the Reproductive Health Act, which repealed many restrictions on abortion.

As of July 3, 2022, Representative Cassidy is a member of the following Illinois House committees:

Cassidy is openly lesbian. Her spouse is Candace Gingrich, who works as a lobbyist for an Illinois-based cannabis company following Cassidy's work to legalize cannabis.