John Anthony Olszewski Jr. also known by his nickname Johnny O, is an American politician who has served as a member of the U.S. House of Representatives from Maryland's 2nd congressional district since 2025. A member of the Democratic Party, he served as the 14th county executive of Baltimore County, Maryland, from 2018 to 2025. A member of the Democratic Party, Olszewski previously served as a student member of the Baltimore County Board of Education from 1999 to 2000, and two terms in the Maryland House of Delegates representing the 6th district from 2006 to 2015. The district covered most of the southeastern portion of Baltimore County, including the town of Dundalk, Maryland. Olszewski unsuccessfully ran for the Maryland Senate in District 6 in 2014, narrowly losing to Republican challenger Johnny Ray Salling. Olszewski became Baltimore County Executive in 2018 after narrowly defeating state senator James Brochin in the 2018 Democratic primary election and defeating former state Insurance Commissioner Alfred W. Redmer Jr. in the general election. Olszewski was re-elected in 2022, defeating Republican nominee Pat McDonough. Olszewski first ran for the U.S. House of Representatives in 2024, defeating state delegate Harry Bhandari in a landslide in the Democratic primary and defeating radio host Kimberly Klacik in the general election. He was sworn in on January 3, 2025.