Ruminants play a significant role in global agriculture, providing essential products like meat and milk. However, their digestive system, particularly their complex gut microbiota, has profound implications for both their efficiency in utilizing feed and their environmental footprint, notably methane emissions. This review delves into the intricate relationship between the gut microbiota of ruminants and its dual impact on digestive efficiency and methane emissions in livestock production systems. The gut microbiota of ruminants, primarily composed of bacteria, protozoa, fungi, and archaea, plays a pivotal role in breaking down complex plant materials into absorbable nutrients. Microbial fermentation within the rumen allows ruminants to derive energy from fibrous feedstuffs that would otherwise be indigestible. However, this fermentation process also produces methane as a byproduct, contributing significantly to greenhouse gas emissions. Understanding the composition and function of the gut microbiota is crucial for improving the efficiency of feed utilization in ruminants. Strategies aimed at modulating the microbiota, such as dietary interventions and microbial additives, offer promising avenues to enhance nutrient utilization and reduce methane emissions simultaneously. For instance, supplementation with specific probiotics or prebiotics can alter microbial populations in favor of more efficient fermentation pathways, thereby improving feed conversion efficiency and decreasing methane production. Furthermore, advancements in microbial genomics and metagenomics have provided insights into the diversity and metabolic potential of rumen microbes, enabling the development of targeted interventions to manipulate the microbiota effectively. However, implementing such strategies on a large scale requires further research to optimize their efficacy, ensure animal health and welfare, and minimize any unintended consequences