Peter William Barca (born August 7, 1955) is an American Democratic politician from Kenosha, Wisconsin. He was the 14th secretary of the Wisconsin Department of Revenue (2019–2024) in the administration of Governor Tony Evers. He was a candidate for U.S. House of Representatives in Wisconsin's 1st congressional district in 2024 losing to incumbent Bryan Steil; he previously represented the district during the 103rd Congress (1993–1995).

Barca also served nine terms in the Wisconsin State Assembly, covering the years 1985 through 1993 and 2009 through 2019, and was elected Democratic floor leader from 2011 through 2017. He represented the north side of the city of Kenosha and part of Somers. Between his stints in the Assembly, he also served as the Midwest Regional Administrator of the U.S. Small Business Administration during the presidency of Bill Clinton.

Barca was born in Kenosha, Wisconsin, on August 7, 1955, and spent his entire youth in the Kenosha area. He graduated from Kenosha's Mary D. Bradford High School in 1973 and went on to earn his bachelor's degree from the University of Wisconsin–Milwaukee in 1977.

After earning his bachelor's degree, he returned to Kenosha and started his career as a teacher for emotionally disturbed children and a team leader for students with special needs, Barca went on to become the director of the Friendship Camp, a camp for children with disabilities.

Barca's work as a teacher led to involvement with the teachers' union and local politics; he soon became active in the Democratic Party of Wisconsin and was elected chairman of the Kenosha County Democratic Party in 1979. He resigned from the office a year later to attend Harvard Graduate School. He ultimately returned to Wisconsin and completed his M.A. in public administration and educational administration from the University of Wisconsin–Madison in 1983. After returning to Kenosha, he was employed at the Kenosha Achievement Center and worked in job placement.

Barca made his first run for public office in 1984. That year, Kenosha's north side state representative, Joseph Andrea, announced that he would run for Wisconsin Senate that fall, creating an open seat in the recently redrawn 64th Assembly district. Barca was one of eight candidates who sought the Democratic nomination in that primary, including former county supervisor David Holtze, former city councilmember Gerald Bellow, former school board member Mark Lindas, former UAW local leader Frank Perone, and city police and fire commission member Marlene Mura. Barca prevailed over the divided field with 34% of the vote. At the time of the primary, Barca and others credited his victory to a strong campaign organization. Barca also acknowledged the popularity of his family name, due to his father's decades operating popular Kenosha restaurants. Barca went on to win the general election with nearly 80% of the vote in the heavily Democratic district.

During his initial tenure in the State Capitol, Barca authored and passed a wide variety of proposals covering issues such as economic development, protection for seniors and the disabled, education, employment and job training, criminal justice, and environmental protection. He also worked closely with the Kenosha delegation to help pass legislation that led to the creation of the Lakeview Corporate Park. Barca also chaired several special legislative committees that led to Wisconsin’s nationally recognized welfare reform program, implemented the award-winning 'one stop shop' employment and training systems, and developed the roadmap for rail services between Kenosha and Milwaukee.

After winning his fourth term in 1990, Barca was elected to a party leadership position in the Assembly, serving as majority caucus chair for the 1991 legislative term. He was re-elected to that leadership position in the 1993 term, but resigned from the Assembly after his election to the U.S. House of Representatives that May.