Dimethylone (βk-MDDMA) is a substituted cathinone derivative with stimulant and empathogenic effects. Unlike the corresponding amphetamine derivative MDDM which is thought to be practically inactive, dimethylone substitutes for methamphetamine and MDMA in animal studies and has been sold as a designer drug.

In the United States, dimethylone is considered a Schedule I controlled substance as a positional isomer of butylone.