Elephant grass (Cenchrus purpureus) is an important forage crop hindered by high lignin content. Although MYB transcription factors (TFs) regulate lignin biosynthesis, their roles in elephant grass remain unclear. In this study, we identified 247 CpMYB TFs through whole-genome bioinformatic analysis of elephant grass and classified them into 23 phylogenetic subgroups. Among them, 233 were mapped to 14 chromosomes, and 14 to unanchored contigs. Gene structure, conserved motifs, and domain analyses revealed subgroup-specific conservation and CpMYB proteins dominated by random coils and α-helices. Gene duplication and selection pressure analyses indicated that segmental duplication predominantly contributed to family expansion. Transcriptome analysis identified 48 CpMYB genes differentially expressed in internodes at least one of three developmental stages, with promoters containing various growth-, phytohormone-, and stress-related cis-elements. Additionally, nine CpMYB genes were consistently differentially expressed across all three stages, and predicted protein–DNA interaction suggested that four of them (CpMYB094, CpMYB131, CpMYB145, and CpMYB148) potentially regulate key lignin biosynthetic genes, including 4-coumarate:CoA ligase 1 (4CL1), hydroxycinnamoyl transferase (HCT), caffeoyl-CoA O-methyltransferase 1/7 (CCoAOMT1/7), and reduced epidermal fluorescence 3 (REF3). However, their regulatory functions require further experimental validation. Overall, this study characterizes the CpMYB family in elephant grass and highlights their potential roles in lignin biosynthesis.