During a study abroad experience on the island of Vieques, Puerto Rico, participants found themselves in an "impromptu learning experience" that extended their learning beyond Puerto Rican culture to real-world debates of tourist development, environmental issues, and the struggles of the native population. In this paper, we introduce impromptu learning: an unplanned experiential learning experience, triggered by a significant and personalized incident, that engages, invigorates, and mobilizes students to seek further learning and knowledge. We used qualitative data in the form of interviews and students' journals to describe and elucidate the characteristics of impromptu learning. Implications of these experiences and their potential for making study abroad as well as learning in other contexts more student-led and more effective for critical consciousness are discussed. In addition, recommendations for supporting and promoting impromptu learning experiences are provided.