Jealousy is an emotion experienced by one who perceives that attention, love or affection is being given to a third party when it should rightfully be given to them. For example, a jealous lover might dislike their partner spending time with other members of the opposite sex, because they feel that they are the rightful sole recepient of their mate's attention.

Jealousy comprises a form of the deadly sin of envy, but implies a feeling of personal claim which isn't present in envy, as well as the requirement of a third person.

The word stems from the French jalousie, formed from jaloux (jealous), and further from Low Latin zelosus (full of zeal), and from the Greek word for "ardour, zeal", with a root connoting "to boil, ferment"; or "yeast "), originally a condition of zealous emulation.