<p>There is an increasing demand for polyurethane (PU) elastomers that integrate high mechanical performance with environmental and economic sustainability to satisfy the demands of advanced applications. However, their development is hindered by a fundamental trade-off: enhancing strength typically compromises toughness, whereas incorporating self-healing capacity often diminishes mechanical robustness. To overcome this challenge, we present a strategy based on an ultrahigh-density hydrogen-bonded network formed at the interface between tannic acid-functionalized cellulose nanocrystals (TA@CNC) and waterborne polyurethane (WPU) matrix. This dynamically cross-linked architecture enables efficient energy dissipation and supports intrinsic self-healing, thereby simultaneously enhancing both mechanical performance and self-healing capacity. The resulting elastomer demonstrates outstanding overall performance, achieving a tensile strength of 48 MPa, an elongation at break of 2667%, a toughness of 700 MJ·m⁻³, a true fracture stress of 1319 MPa, and a room-temperature self-healing efficiency of 84%. The design strategy presented here opens new avenues for developing polyurethane elastomers with simultaneously enhanced mechanical performance and self-healing capacity, effectively paving the way for their application in demanding and sustainable scenarios.</p>