Plasmonic tunnel junctions are metal-insulator-metal structures with a nanoscale dielectric gap that can simultaneously support surface plasmons and electron tunneling. The extremely strong confinements and interactions of electrons, plasmons, and photons in the junctions provide a novel platform, merging electronics and photonics for studying and manipulating electrons and photons at the nanoscale. In this review, the recent progress in the field of plasmonic tunnel junctions is overviewed as concerns their applications in plasmon/light generation and plasmon/light-electron conversion.