The ionones, from greek ἴον ion "violet",[1] are a series of closely related chemical substances that are part of a group of compounds known as rose ketones, which also includes damascones and damascenones.

β-Ionone is a significant contributor to the aroma of roses, despite its relatively low concentration, and is an important fragrance chemical used in perfumery.

[3][4] The carotenes α-carotene, β-carotene, γ-carotene, and the xanthophyll β-cryptoxanthin, can all be metabolized to β-ionone, and thus have vitamin A activity because they can be converted by plant-eating animals to retinol and retinal.

[5] The same study also discovered that carotenoid content, volatile emissions, and OfCCD1 transcript levels are subject to photorhythmic changes, and principally increased during daylight hours.

[5] Ionone can be synthesised from citral and acetone with calcium oxide as a basic heterogeneous catalyst and serves as an example of an aldol condensation followed by a rearrangement reaction.