The recent discovery of over 40 ultra-high-energy (UHE; > 100 TeV) gamma-ray sources and neutrino emission in the Galactic Plane has provided compelling evidence for Galactic PeVtrons, which are capable of accelerating particles to 10^15 eV or beyond. These findings mark a significant paradigm shift in high- energy astrophysics from ``Do PeVatrons exist in our galaxy?" to ``What are the Galactic PeVatrons?” As evident from previous studies of Galactic TeV sources, multi-wavelength observations are crucial to identifying the Galactic PeVatrons. In particular, a combination of broadband spectral energy distribution (SED) and morphological data can serve as a powerful diagnostic tool for probing their particle acceleration and emission mechanisms. This presentation will review recent multi-wavelength observation campaigns of Galactic PeVatron sources, primarily focusing on X-ray observations combined with radio, GeV, and TeV data. I will highlight (1) multi-epoch NuSTAR hard X-ray observations of young supernova remnants, (2) multi-wavelength observations of pulsar wind nebulae associated with UHE sources, (3) X-ray observations of other PeVatron accelerators (the Galactic Center, TeV binaries, microquasar jets, star clusters etc.), and (4) X-ray surveys of unidentified UHE sources, including the so-called dark accelerators, as well as the prospects in X-ray astrophysics of Galactic PeVatrons.