We use Angle Resolved Photoemission Spectroscopy (ARPES), Raman spectroscopy, Low Energy Electron Diffraction (LEED) and x-ray scattering to reveal an unusual electronically mediated charge density wave (CDW) in K$_{0.9}$Mo$_6$O$_{17}$. Not only does K$_{0.9}$Mo$_6$O$_{17}$ lack signatures of electron-phonon coupling, but it also hosts an extraordinary surface CDW, with T$_{S\_CDW}$=220\,K nearly twice that of the bulk CDW, T$_{B\_CDW}$=115\,K. While the bulk CDW has a BCS-like gap of 12\,meV, the surface gap is ten times larger and well in the strong coupling regime. Strong coupling behavior combined with the absence of signatures of strong electron-phonon coupling indicates that the CDW is likely mediated by electronic interactions enhanced by low dimensionality.