The simplest diene is 1,3-butadiene:
The 1,3 configuration of double bonds found in 1,3 butadiene (conjugated double bonds) make these types of dienes capable of participating in more reaction types than is the case for molecules with either just a single alkene functional group or with multiple, but non-alternating, alkene groups. One possible reaction for diens is the Diels-Alder reaction.
A compound in which two double bonds exist but are immediate adjacent to each other is, in contrast, called an allene.
cyclopentadiene is another example of a diene.