Lake Darby is an unincorporated community and census-designated place in Franklin County, Ohio, United States, located mostly in Prairie Township and partly in Brown Township.

Lake Darby is located in western Franklin County.

Big Darby Creek, a tributary of the Scioto River, forms the western border of the CDP as well as the Franklin County/Madison County line.

The village of West Jefferson lies directly across the creek from Lake Darby.

U.S. Route 40 (National Road), a four-lane highway, forms the southern edge of the community, leading east 13 miles (21 km) to downtown Columbus and west 31 miles (50 km) to Springfield, Ohio.

10.1% of all households were made up of individuals, and 0.5% had someone living alone who was 65 years of age or older.