Nanotechnology is a science that deals with the design, characterization, synthesis, and application of nanoscale materials (1–100 nm). Nanomaterials (NMs) have unique physicochemical characteristics, including ultra-small size, large surface area to mass ratio, and high reactivity. Nanomedicine is the application of nanotechnology in medicine to advance diagnostic, preventive, and therapeutic strategies. The potent antioxidant properties of some NMs open the door to develop new therapies with enhanced, targeted actions. However, oxidative stress is the main adverse effect of metallic oxide NMs, such as nickel oxide, zinc oxide, and titanium dioxide. Therefore, NMs have double-edged effects on cellular redox hemostasis. Recently, many researchers have focused on the ecological and safety issues of synthetic NMs to reduce the risk of their toxicity. The present special issue “Advances in Nanotechnology, Nanopollution, Nanotoxicology and Nanomedicine (ANNNN)” is dedicated to integrate the previous and the current biological, medical, and ecological data on NMs.