To live an 'authentic life' amidst the personal and cultural connections of the globalising world demands a particular form of human 'being', referred to as 'global citizenship'. Global citizen 'becoming' is a process of mundane and profound change to our sense of self-in-the-world and our abilities to act-in-the-world. Such change occurs when 'outer world' intrusions interrupt the coherence of the lifeworld. Previous student mobility research and theory reveal potentially rich sites for significant personal change. Can such experiences contribute specifically to global citizen being and becoming? Utilising the tools of phenomenology, we explore the lived-experience of UK undergraduate students across a number of different international mobility activities and witness the uniqueness of individual experience and learning, hitherto un-remarked forms of intersubjectivity, and multi-dimensional learning which leads to lifeworld change.