This dissertation is a systematic study of the semantics of mirativity, a descriptive category for surprise-related meanings and their expression in natural language. Building on both typological and formal research traditions, I argue for a concerted research program for investigating this domain of meaning. Specifically, I address three foundational questions: (i) what is mirativity (semantic identity); (ii) what is the content of mirative meaning, and (iii) how does mirative meaning arise from evidential meaning.Despite a strong intuition that linguistic expressions of surprise form a natural category (mirativity), existing literature has persistently faced a certain amount of ambiguity over the definition and usage of this notion. I first resolve this ambiguity by articulating a semantic definition of mirativity grounded in the cognitive science of SURPRISE: mirativity is a range of attitudes which characterize mental states induced by the experience of SURPRISE. These atti- tudes necessarily contain a dimension of either novelty or counterexpectation: the latter causally induces SURPRISE, and the former is a necessary condition of the latter. Second, previous work has shown mirative meaning to have either propositional or speech act-level content. I argue that there is a third typological possibility: novel data on the mirative marker yikaon in Shanghai Wu (Sinitic, China) show that the content of a mirative attitude can be the union of a set of propositions: such miratives can crucially predicate an attitude over both single propositions in the declarative and questions with non-trivial informative content. I analyze this mirative contribution as an emotive attitude update to the speaker’s Discourse Commitments, which scopes over sentential force. Third, across languages, mirative markers are often also evidentials. I argue that the semantic affinity between evidentiality and mirativity has diverse theoretical characters: indirect, reportative and inferential evidentials do not evoke mirative meaning in the same way. Specifically, I argue that the connection between reportative evidentiality and mirativity can be due to diachronic reanalysis. Reportatives frequently trigger Conversational Implicatures about the SPKR’s attitude because they encode perspectivally asymmetric Discourse Commitments and QUD-addressing proposals. I argue that reportatives are often reanalyzed as SPKR-attitude markers due to the conventionalization of such Conversational Implicatures, driven by a principle of EPISTEMIC TRANSPARENCY.