Long regarded by US legal scholars as uninteresting, private law theory has received renewed attention in the United States and around the world. Yet, even amid this scholarly revival, private law is still too often reduced to the more traditional concepts found within tort, property, and contract law. These basic categories alone cannot provide sufficient basis for informed doctrinal analysis - lawyers who hope to apply private law theory must also understand the rules and concepts that operate independently of, across, or within the interstices of these fields. The essays collected in Interstitial Private Law encourage the next generation of private law theorists to engage with the 'connective tissue' of private law. Internationally prominent scholars introduce and analyze these crucially important interstitial aspects, including legal personhood, agency and other attribution rules, consent, estoppel, equity, remedies, and restitution. Contributions explain what interstitial concepts are and explore the ways they operate, contributing to the systematicity and functional coherence of private law systems. In doing so, Interstitial Private Law broadens and deepens the scholarly agenda for private law theory in the United States and worldwide.