Truthfulness may refer to:
- Honesty - a moral character of a human being, related to telling the truth
- Accuracy - the propensity of information to be correct
- Strategyproofness - a property of a mechanism in game-theory, related to encouraging the participants to act according to their true preferences.
- Truth - a concept most often used to mean in accord with fact or reality.
- Truthiness - a quality characterizing a "truth" that a person making an argument or assertion claims to know intuitively.
- Truthlikeness - a philosophical concept that distinguishes between the relative and apparent truth and falsity of assertions and hypotheses.