In this chapter, we review the taxonomy, phylogeography and evolutionary history of the molids (Tetraodontiformes: Molidae), focusing on the contributions provided by molecular genetics. Studies using the mitochondrial genome have confirmed the phylogenetic topology of the Molidae genera hypothesized from morphological studies (Ranzania-basal, Masturus-intermediate, Mola-derived). Mitochondrial DNA identified a Mola clade that subsequently facilitated the description of M. tecta, the first novel molid species in over 125 years. To resolve the taxonomy of the ocean sunfish (M. mola) and the bump-head sunfish (M. alexandrini) we sequenced the hypervariable mitochondrial d-loop region and conducted phylogenetic analyses on a population of molids from Ceuta, Spain that possesses both a bump-head and a trait unique to M. mola—the wavy clavus. In addition, we sequenced Mola and Ranzania spanning the Pacific and Atlantic ocean basins to assess phylogeographic structure within these taxa. Bump head, wavy clavus Ceuta molids were genetically identified as M. mola, supporting a proposed change of the "bump-head" common name to simply giant ocean sunfish. Atlantic and Pacific molids mostly grouped into respective geographic clades, but further population genetic studies are needed to tease out patterns of gene-flow and distribution. To that end, we summarize the numerous genetic and genomic tools available to inform molid biology and monitoring efforts moving forward. Lastly, we discuss the genome contents and patterns of selection in the recently sequenced Mola mola genome.