Conjugative plasmids are able to disseminate antimicrobial resistance genes amongst a broad range of bacterial hosts, including pathogens that cause infections in humans and animals. To investigate the diversity of IncA/C and IncI1 plasmids amongst Gram-negative bacteria, plasmid and whole-genome sequence data were analysed via multi-locus sequence typing and phylogenetic analysis of core and common genes. The data show these two plasmid types, which both contribute to dissemination of antimicrobial resistance, differ in their geographical distribution and bacterial host range.