The Third in a series of FACET-II Science Workshops was held at SLAC National Accelerator Laboratory on October 17-20, 2017 [ ]. The workshop drew sixty-four participants from twenty-three different institutions including ANL, BNL, DESY, DOE, Ecole Polytechnique, FNAL, IST, JAI, LBNL, Princeton, Radiabeam, Radiasoft, SLAC, Stony Brook, Tech-X, Tsinghua University, UC Boulder, UCLA, UT Austin, University of Chicago, University of Oslo, University of Pennsylvania, University of Strathclyde and University of Victoria. The 2015 workshop [ , ] helped prioritize research directions for FACET-II. The 2016 workshop was focused on understanding what improvements are needed at the facility to support the next generation of experiments [ , ]. The focus of the 2017 workshop was to assess and chart the development of key technologies needed to execute the envisioned FACET-II science program. Show Partial Abstract