Multiple studies have analysed the composition of the human gut microbiota using culturing and sequencing methods, but a comprehensive catalogue remains elusive. A new study used 13,133 human gut metagenomic data sets from 75 different studies and reconstructed 92,143 metagenome-assembled genomes from 11,850 human gut microbiomes. Further analysis revealed 1,952 uncultured candidate bacterial species currently absent from high-quality human-specific databases, expanding phylogenetic diversity of the known species repertoire by 281%. The data also improve classification by >200% of less-well-studied samples from Africa and South America. In addition, the new candidate species contain a multitude of new biosynthetic gene clusters and have distinct functional repertoires.