Plants must continuously adapt to their biotic and abiotic environment in order to survive, grow, and reproduce. Redox reactions play a central role in these processes, influencing numerous aspects of plant physiology, from transcriptional regulation to environmental perception, through the modulation of cellular metabolism. Redox regulation is driven by changes in the concentrations of reactive oxygen and nitrogen species (ROS/RNS), as well as antioxidants, which impact plant functioning. In this Special Issue, a collection of reviews and articles cover current work in this field, exploring the role of redox molecules in plant metabolism and adaptation, spanning from detailed molecular mechanisms to whole-plant responses.