Although assertions are often characterised as essentially informative speech acts, there is a widespread disagreement concerning how the informativeness of assertions should be understood. This paper proposes the informativeness norm of assertion, which posits that assertions are speech acts that essentially deliver new information. As a result, if one asserts something that is already commonly known, one’s assertion is improper. The norm is motivated by appealing to unique conversational patterns associated with informative and uninformative uses of assertions, an analogy between (...) assertions and inquiries, and a distinction between assertions and uninformative speech acts. By focusing on the normative approach to speech acts, the paper discusses how particular norms of assertion deal with the data supporting the norm of informativeness. To be informative, the speaker must consider the epistemic position of the audience. Since the majority of norms proposed in the literature are speaker-centred, they fail to explain the submitted data. Looking more broadly, focusing on the informativeness of assertions underscores the crucial role of the audience in construing adequate speech act accounts. (shrink)