Foundational Papers in Complexity Science maps the emergence of complex-systems science over the last century. This four-volume set unites, for the first time, dozens of articles published in a variety of academic journals in a timely reminder that complexity knows no disciplinary boundaries. Edited and curated by Santa Fe Institute President David Krakauer, this comprehensive collection of papers aims to help readers understand the history, current state, and future of complexity science. More than a compilation, Foundational Papers reflects large-scale collaboration within the SFI community, as contemporary researchers introduce and contextualize the work that shaped their own. In the process, they reveal how complexity shatters the usual scientific divisions. Join the Santa Fe Institute in a look back at the path complexity science has followed, as we move toward a clearer view of what lies ahead.