The 27th European Association of Computer-Assisted Language Learning (EUROCALL) conference was hosted by UCLouvain in Louvain-la-Neuve (Belgium), in collaboration with KU Leuven, from the 28th to the 31st of August 2019. The theme selected for the 2019 EuroCALL conference held in Louvain-la-Neuve was "CALL and complexity." As languages are known to be intrinsically and linguistically complex, as are the many determinants of learning (additional) languages, conference organizers wanted to view complexity as a challenge to be embraced collectively. The 2019 conference paid tribute to providers of Computer Assisted Language Learning (CALL) solutions and recognized the complexity of their task, acknowledged the notion of complexity to ensure the provision of ad hoc CALL solutions, and drew both learners' and teachers' attention to complexity issues so that they can make the most of their learning/teaching experience. The conference program included 189 paper presentations, 4 symposia, 10 workshops, and 46 posters. All of these activities were divided into the following sub-themes in CALL: social inclusion, computer mediated communication and telecollaboration, corpora and language learning, digital bi- and multi-literacies, digital game-based language learning, intelligent CALL, mobile assisted language learning, natural language processing applications, open educational resources and practices, research trends, second language acquisition principles, task complexity, teacher education and professional development, the complexity, accuracy, and fluency framework, and virtual reality and gamification.