Crotonaldehyde (E,E)-2,4-Decadienal cis-3-Hexenal, also known as (Z)-3-hexenal and leaf aldehyde, is an organic compound with the formula CH3CH2CH=CHCH2CHO.

It is a colorless liquid and an aroma compound with an intense odor of freshly cut grass and leaves.

[1][2] It is one of the major volatile compounds in ripe tomatoes, although it tends to isomerize into the conjugated trans-2-hexenal.

[3] It is produced in small amounts by most plants and it acts as an attractant to many predatory insects.

It is also a pheromone in many insect species.