Landen is a census-designated place (CDP) in Deerfield Township, Warren County, Ohio, United States. The population was 12,766 at the 2000 census. It is located around Columbia Road and Montgomery Road in the southeastern part of the township. It surrounds Twenty Mile Stand and near Fosters.
Landen was named after Theodophilus James Landen, an early Ohio settler who owned the farmland surrounding Twenty Mile Stand. The man-made Landen Lake occupies the center of the residential area in the town. Though its formal place designation is "Landen Farm Drainage Lake", the reduction in farming activity in the immediate area of the lake has made it suitable for recreation. The lake was further improved with the completion in 2008 of a major dredging operation  that removed 184,000 cubic yards of sediment from the lake.