Rumen microbiota transplantation (RMT) is garnering increasing attention as a strategy to modulate the rumen microbiome in ruminants, aiming to improve animal health and production performance. This review systematically evaluates RMT research published over the past two decades across diverse ruminant species and production systems. Based on our systematic literature analysis of over 200 publications, which distinguishes between controlled trials and observational studies, we find that in controlled trials, RMT can enhance feed efficiency (range: 5-15%) and reduce methane emissions (range: 10-30%) in beef and dairy cattle. Observational studies report a wider range, with some showing improvements up to 20% in feed efficiency and 35% in methane reduction, but these are subject to greater confounding factors. Others report limited or adverse effects, with outcomes varying substantially based on donor selection, transplant dosage, administration routes, and recipient physiological status. Currently, RMT research remains in early stages with significant methodological variations. Although existing evidence supports its efficacy, substantial gaps persist in understanding its mechanisms. This review synthesizes current knowledge on rumen microbiota succession patterns, critically evaluates existing RMT studies, and reconciles inconsistent findings by examining methodological variations and contextual factors. We propose a comprehensive mechanistic framework integrating microbial colonization, competitive exclusion, metabolic remodeling, and immune regulation. Furthermore, we explore the potential of utilizing co-evolved natural microbial communities as transplant material, representing a paradigm shift from conventional probiotic approaches toward ecosystem-level interventions. As our understanding deepens, RMT holds promise as a valuable tool for sustainable livestock production. Nevertheless, ongoing research remains crucial to elucidate dose-response relationships, establish evidence-based standardized protocols, and validate long-term efficacy and safety.