Diane Lynn Harkey (born June 20, 1951) is an American politician who served as a member of the California State Board of Equalization, representing its fourth district from 2015 to 2019. A member of the Republican Party, she was previously elected to the Dana Point City Council (2004–2008), including a stint as Mayor of Dana Point (2007–2008), as well as the California State Assembly (2008–2014). She was a Republican candidate for California's 49th congressional district seat in the 2018 election, losing to Democrat Mike Levin.