Polysaccharide-based nanogels have drawn considerableinterest in pharmaceutics because of their superior biocompatibility andpotential responsiveness to external stimuli, enabling specific drug release.During the fabrication of nanogels, however, covalent cross-linking ofteninvolves less friendly cross-linkers and traditionally employed noncovalentcross-linking often relies on weak interactions that may lead to prematurepayload release. Herein, we report host−guest chemistry-driven supra-molecular chitosan nanogels (CNGs) that are responsive to eitherendogenous or exogenous stimuli, thus allowing selective drug release inspecific cancer cells or disease sites. In an aqueous solution, two phenylalanine(Phe) units of Phe-grafted chitosan (CS-Phe) were encapsulated into onecavity of cucurbit[8]uril (CB[8]), driving cross-linking of CS-Phe and formation of CNGs. Doxorubicin hydrochloride (DOX),a chemotherapeutic agent, was entrapped in the matrix of CNGs during the formation of nanogels to yield DOX−CNGs withan excellent drug loading efficiency. The morphology and size of CNGs were fully assessed by transmission electron microscopyand dynamic light scattering. The encapsulated DOX was selectively liberated in the presence of competitive guests of CB[8],such as endogenous spermine (SPM) that is overexpressed by certain types of cancer cells or exogenous amantadine (ADA)that may be added into cells or tissues that require targeted treatment, either of which may replace Phe from the cavity of CB[8]resulting in the breakdown of the nanogels and payload release. The CNGs were efficiently internalized by cells, and the DOX−CNGs exhibited specific, potent activity against cancerous cells such as A549 cell line that is well known for SPMoverexpression. This study reports that thefirst stimuli (competitive guest)-responsive host−guest interactions initiatedsupramolecular CNGs with excellent biocompatibility and selective therapeutic efficacy against cancer cells. It may provide newinsights into the design and fabrication of novel stimuli-responsive payload delivery systems.