In chemistry, methylene is a divalent functional group CH₂ derived formally from methane. The name "methylene" is used for two types of groups:

• -CH₂- group (bound by two single bonds) present e.g. in dichloromethane (alternative name is methylene chloride)
• =CH₂ group (bound by one double bond), present e.g. in formaldehyde (can be named methylene oxide, but it is not used/recommended). The better example is methylenecyclopropene.

Methylene is also a name for

• unstable electrically neutral species :CH₂, the simplest carbene.

Functional groups