Cruelty is the pleasure in inflicting suffering or inaction towards another's suffering when a clear remedy is readily available. Sadism can also be related to this form of action or concept. Cruel ways of inflicting suffering may involve violence, but affirmative violence is not necessary for an act to be cruel. For example, if a person is drowning and begging for help and another person is able to help with no cost or risk, but is merely watching with disinterest or perhaps mischievous amusement, that person is being cruel—rather than violent.

George Eliot stated that "cruelty, like every other vice, requires no motive outside itself; it only requires opportunity." Bertrand Russell stated that "the infliction of cruelty with a good conscience is a delight to moralists. That is why they invented Hell." Gilbert K. Chesterton stated that "cruelty is, perhaps, the worst kind of sin. Intellectual cruelty is certainly the worst kind of cruelty."

The word has metaphorical uses, for example, "The cliffs remained cruel." (i.e., unclimbable when they desperately needed to be climbed) in The Lord of the Rings.