Douglas Earl Applegate was an American politician who served in the United States House of Representatives from Ohio's 18th congressional district from 1977 to 1995, as a member of the Democratic Party. Prior to his tenure in the United States House of Representatives he served in the Ohio House of Representatives from 1961 to 1968, and in the Ohio Senate from 1969 to 1974.

The 18th congressional district of Ohio is an obsolete congressional district last represented by Republican Bob Gibbs. The district voted for the majority party in the House of Representatives in every election since 1954.