We report the synthesis of ultrasmall nanogels (Rg < 6 nm) from branched and hyperbranched cyclic polyglycerols (Mn = 3–200 kg/mol) via intramolecular cross-linking with diboronic acids (benzene-1,4-diboronic acid, Bz-2B, and [(1,2-diphenylethene-1,2-diyl)bis(4,1-phenylene)] diboronic acid, TPE-2B) through dynamic covalent bonding. Structural analysis by small-angle X-ray scattering revealed a clear architecture–conformation relationship: high-molecular-weight hyperbranched cyclic polyglycerols