Understanding quantum many-body systems with strong interactions and unconventional phases therein is one of the most challenging tasks in physics. In cold atom physics, this has been a focused research topic for nearly two decades, where strong interactions are naturally created and well manipulated by bringing the system close to a scattering resonance. However, most of the studies thus far have been limited to the s-wave resonance. Here, we report the experimental observation of a tunable and broad d-wave shape resonance in a quantum degenerate 41K gas, hallmarked by the fact that the molecular binding energies are split into three branches. The measured lifetime in the resonance regime is found to be much longer than the characteristic timescale for many-body relaxations. The analysis of the breathing mode, excited by ramping through the resonance, suggests that a low-temperature atom–molecule mixture is produced. Our system offers great promise for studying a d-wave molecular superfluid.