Earlier analyses evaluating patterns of gut microbiota in individuals from different geographies and age groups are heterogeneous in methodology, precluding broader conclusions about the relationship between the gut microbiome and geographic region, age, and clinical health. Here, we systematically conducted a meta-analysis of 16s rRNA gut microbiome sequencing data representing 10,878 samples across North America, Europe, Africa, Asia and Oceania. Our analysis included 27 countries and three age groups (neonate to age 17, or AG01; ages 18 to 64, or AG02; 65 and above, or AG03). We identified that Firmicutes, Bacteriodetes, and Proteobacteria constitute core phyla across geographic regions. A differing predominance of top families alongside core family Lachnospiracaeae across regions comprised unique microbiome signatures. Countries also differed in their relative abundances of Bifidobacterium, Faecalibacterium, Lactobacillus and Bacteroides. We found in our age analyses that Proteobacteria and Actinobacteria were the most abundant phyla in AG01, and Actinobacteria abundance declined across all continents with increasing age. The relative abundance of Bacteriodetes increased between AG01 and AG02. Enrichment of asthma-associated Enterobacterieaceae in AG01 was highest for North America, followed by Europe and then in Asia. We discuss the correlation of these gut microbial patterns in the context of dietary patterns, populations health, clinical health trends, and healthy aging.