Plant diversity shapes far more than the appearance of ecosystems—it fundamentally alters how herbivores find, feed on, and interact with their hosts. Effects of Plant Diversity on Plant–Herbivore Interactions shows how mixed plant communities reduce herbivore damage through associational resistance, disrupt the cues herbivores rely on, and support populations of natural predators and parasitoids. Diverse ecosystems also harbor a broader range of defensive traits, strengthening plants’ collective resilience to herbivory. Despite decades of research, important questions remain. How do specific combinations of plant species and traits influence herbivory under different environmental conditions? What roles do complex tri trophic interactions—among plants, herbivores, and predators—as well as belowground communities play in shaping these outcomes? And how can these insights be translated into predictive models that inform forest management, agriculture, and conservation?This book addresses these gaps through a focused, integrative approach that sets it apart from broader ecosystem function literature. It offers a comprehensive examination of how plant diversity influences herbivore behavior, plant defense strategies, and ecosystem stability, moving beyond single species perspectives. Drawing on forests, grasslands, and agricultural systems, the volume integrates theory and empirical evidence to illuminate multilevel trophic networks that are often overlooked yet critical for ecosystem resilience. Grounded in real world case studies, it also demonstrates how principles of plant diversity and herbivore regulation can be applied to enhance ecosystem health, build resilience, and guide sustainable management under climate change. Clear, timely, and interdisciplinary, Effects of Plant Diversity on Plant–Herbivore Interactions is an essential resource for researchers, practitioners, and managers seeking to understand—and manage—the complex biological relationships shaping natural and agricultural landscapes.