Native-speakerism is the main goal of the monolingual approach to language education. In an attempt to challenge native-speakerism as a dominant ideology in English language education, this study probed into language learners' experience of authenticity through an existential framework, comprising the two concepts of resoluteness and self-other relations, which was derived from Heidegger's (1962) concept of authenticity in "Being and Time." To collect data, a group of English language learners studying at Iranian state universities were investigated by the administration of semi-structured interviews. The analysis of data led to the emergence of three core themes: epistemological and ontological engagement, agency for response-ability, and the process of in-situ knowing. Indeed, the collected data demonstrated a shift of emphasis on authenticity from native-speakerism towards the realities of language learning where the possibility of being rendered capable can be provided, and space is offered for the integration of mainstream epistemology and learners' ontology through in-situ knowing. More importantly, the existential interpretation of authenticity, proposed in our study, was revealed to be an inclination towards bi/multilingualism.