0_8335 Unconventional superconductivity is known for intertwining with other correlated states such as antiferromagnetic, nematic, and charge orders, and finding new intertwined orders is highly important in understanding the mechanism of unconventional superconductivity. Specifically, antiferromagnetic and nematic orders are widely observed in the iron-based superconductors (FeSCs). However, evidence for charge density wave (CDW) order in the phase diagrams of FeSCs is rarely found. Employing low temperature scanning tunneling microscopy and density function theory, here we demonstrate, through expanding the phase diagram of Ba1-xKxFe2As2 to the heavily hole doped regime beyond KFe2As2 by surface doping, the formation of a CDW order on the As-terminated surface of Ba0.23K0.77Fe2As2. The CDW formation is accompanied by the disapperance of superconductivity, indicating their direct competing relationship. More importantly, the CDW wavevector matches well with the nesting vector between the near-EF saddle points, providing hitherto compelling evidence for the saddle-point-driven CDW, a mechanism predicted by Rice and Scott 48 years ago. Our findings offer new insights into the superconductivity and intertwined orders of iron pnictides and provide an intriguing platform for investigating their correlated states at the doping levels closer to the half-filled configuration (d5).