Functional RNAs in Plants explores the rapidly advancing field of plant RNA biology and its transformative role in modern agriculture. Covering microRNAs, small interfering RNAs, long noncoding RNAs, circular RNAs, and CRISPR-associated RNAs, the book explains their identification, design, structural and functional analysis, and applications in crop improvement. Chapters address both abiotic and biotic stresses, highlighting how functional RNAs regulate tolerance to climate-driven challenges as well as plant–microbe interactions and disease resistance. Technical sections detail progress in bioinformatics, integrated multi-omics, spatial and single-cell approaches, and high-throughput transcriptomics, which together provide new insights into RNA networks underlying plant stress responses. The book also discusses artificial small RNAs, secondary metabolism, and competing endogenous RNA systems, connecting mechanistic understanding with applied breeding strategies. Practical guidance is offered on integrating RNA knowledge into smart breeding, sustainable agriculture, and CRISPR-based innovations, with emphasis on designing and delivering functional guide RNAs for crop improvement. By combining foundational concepts with emerging applications, this volume serves as a valuable reference for academics, researchers, and advanced-level students in plant molecular biology and agricultural biotechnology.