John Anthony Olszewski Jr., also known by his nickname Johnny O, is an American politician and the current Baltimore County Executive. He previously served two terms in the Maryland House of Delegates representing District 6.

The Baltimore County Executive is the highest elected official representing the government of Baltimore County, Maryland, United States. The office was established with the implementation of the county charter for Baltimore County on November 6, 1956. The county executive is elected to post every four years, coinciding with the elections for the county council and governor of Maryland.