The Fibrobacteres phylum contains only two characterised species, Fibrobacter succinogenes and F. intestinalis, both of which are important degraders of cellulose in the mammalian gut. Fibrobacters were though t to be restricted to the gut environment, but this was recently disproven via the detection of novel Fibrobacter spp. in landfill sites and freshwater lakes, with the implication that the distribution and diversity of members of the genus Fibrobacter is poorly understood. Here, the environmental distribution of members of the genus Fibrobacter was addressed; a total of 64 samples from contrasting environments were screened for the presence of Fibrobacter spp. via genus-specific 16S rRNA gene PCR primers. Fibrobacters were detected in 23 samples, with the first specific detection of fibrobacters in marine and estuarine sediments, and Arctic cryoconite. Phylogenetic analysis of 16S rRNA gene sequences revealed 63 Fibrobacter OTUs at 95% sequence similarity, representing a wealth of unclassified species contained within this genus. To address the lack of cultivated Fibrobacter isolates, their isolation from landfill leachate microcosms containing either Avicel or dewaxed cotton string as the sole carbon source for growth was attempted, resulting in the first isolation of F. succinogenes from a landfill site, and the first isolation of fibrobacters from outside the mammalian gut. This is the first phenotypic evidence that fibrobacters are active members of the landfill cellulolytic community. The importance of fibrobacters in landfill cellulose decomposition was further characterised via 454 pyrosequencing of 16S rRNA gene amplicons and shotgun metagenomic sequencing of heavily-degraded cotton samples from landfill leachate microcosm, where fibrobacters have previously been shown to predominate. Fibrobacter 16S rRNA gene amplicons were enriched on the heavily degraded cotton sample (14.2% of sequences, vs. 0.02% for a poorly degraded cotton sample), and metagenome sequencing of the heavily degraded cotton revealed that proteins most closely related to F succinogenes strain S85 dominated the sequence output. Attempts to isolate Fibrobacter spp. from the same heavily degraded cotton sample revealed that Fibrobacters pp. were present in co-culture with Clostridium sporogenes, but attempts to purify these strains were unsuccessful. These data represent a significant contribution to our understanding of the ecology of members of the genus Fibrobacter, and their important role in the hydrolysis of cellulolytic biomass.