Plasmonics constitutes a major branch of nanophotonics. It has inspired a myriad of theoretical studies and experimental applications, such as wave guiding, sensing, imaging, surface-enhanced Raman scattering, etc. By confining electromagnetic waves in ultra-small volumes, surface plasmon polaritons strongly enhance light-matter interactions, which in turn lead to giant nonlinear and nonclassical effects in the plasmonic systems. This session focuses on the nonlinear and nonclassical effects in the plasmonic systems, from both theoretical and experimental points of view. Example topics include second- or third-harmonic generation and Kerr effects from plasmonic structure, nonlocality, electron-spill-out, and electron tunneling in plasmonic structure at the mesoscopic scale.