The evolutionary placement of cetaceans (Cetacea) among artiodactyl mammals has been a major question in mammalian systematics. Historically, cetaceans were commonly classified as a separate order, but molecular, genomic, and paleontological studies have increasingly supported their placement within the artiodactyl lineage and a close sister-group relationship between cetaceans and hippopotamids. This phylogenetic inference should be distinguished from the separate question of the preferred name and taxonomic rank of the encompassing group: both Cetartiodactyla and Artiodactyla are used in the literature, and their use does not imply universal agreement on rank or nomenclature. This narrative review examines morphological, fossil, molecular, behavioral, and phylogenomic evidence concerning cetacean–artiodactyl relationships. It focuses on the historical development of competing hypotheses, the contribution of independent evidence, the placement of key fossils, and the distinction between phylogenetic inference and taxonomic naming. The reviewed evidence broadly supports the placement of cetaceans within the artiodactyl lineage and their close relationship to hippopotamids, while relationships involving some extinct taxa remain sensitive to data and analytical choices. Fossil cetaceans from the Eocene represent diverse branches and combinations of traits and should not be interpreted as a simple sequence of direct ancestors. The review emphasizes transparent taxonomic conventions and the integration of multiple evidence sources in evolutionary systematics.