Together, PFS and hyper suprime-cam (HSC)2 comprise the Subaru measurement of the images and redshifts project. PFS will accomplish the spectroscopic aspect of this project, and HSC has been implementing the imaging part since first light in 2012. The scientific case for the PFS surveys is described in an earlier paper.3 PFS has now entered the construction phase, and Fig. 2 shows the integration and test flow. Generally speaking, PFS comprises two main components: the prime focus instrument (PFI) and the spectrographs, with the fiber system connecting the two parts. This paper provides the first technical overview of the instrument, describing the essential components as well as their intensive test results. Further details on individual PFS components can be found in separate, component-specific SPIE conference papers viz.: fiber system,4–9 fiber positioner10 and prime focus instrument,11 spectrograph,12–14 Dewar and detector,15–18 and metrology camera.19 The subsystems are discussed in roughly the same order as the science light path through the instrument. The Subaru telescope and WFC focus light through a microlens; this microlens, which is described in Sec. 2.1, increases the of the beam to ease the design requirements on the spectrographs. The light then enters the multimode fibers, which are part of a fiber system described in Sec. 2.2 that also includes connectors and fiber arrays. In the telescope focal plane, these fibers are mounted in a series of positioners, described in Sec. 2.3, which connect the fibers to the celestial images. The fibers transmit the science light to one of the four spectrograph modules, described in Sec. 2.4. The spectrograph modules also provide a means for back-illumination, which enables the metrology camera system, described in Sec. 2.5, to measure the positions of the fibers. The relevant software and observational execution processes are described in Sec. 2.6. PFS technical first light is scheduled on Subaru in early 2018 with the start of the associated Subaru strategic program survey expected in 2019.