C. elegans develops through four larval stages that are rhythmically terminated by molts, that is, the synthesis and shedding of a cuticular exoskeleton. Each larval cycle involves rhythmic accumulation of thousands of transcripts, which we show here relies on rhythmic transcription. To uncover the responsible gene regulatory networks (GRNs), we screened for transcription factors that promote progression through the larval stages and identified GRH‐1, BLMP‐1, NHR‐23, NHR‐25, MYRF‐1, and BED‐3. We further characterize GRH‐1, a Grainyhead/LSF transcription factor, whose orthologues in other animals are key epithelial cell‐fate regulators. We find that GRH‐1 depletion extends molt durations, impairs cuticle integrity and shedding, and causes larval death. GRH‐1 is required for, and accumulates prior to, each molt, and preferentially binds to the promoters of genes expressed during this time window. Binding to the promoters of additional genes identified in our screen furthermore suggests that we have identified components of a core molting‐clock GRN. Since the mammalian orthologues of GRH‐1, BLMP‐1 and NHR‐23, have been implicated in rhythmic homeostatic skin regeneration in mouse, the mechanisms underlying rhythmic C. elegans molting may apply beyond nematodes. Synopsis: Development of C. elegans through four larval stages involves rhythmic accumulation of thousands of transcripts during each cycle. Here, this is shown to depend on rhythmic transcription involving the Grainyhead/LSF transcription factor GRH‐1. Rhythmic RNA polymerase II recruitment drives widespread oscillatory gene expression coupled to molting in C. elegans larvaeA genetic screen identifies six transcription factors as candidate core oscillator and molting clock genes, including GRH‐1GRH‐1 accumulates prior to each molt and depletion extends molt durations, impairs cuticle integrity and shedding, and causes larval deathGRH‐1 preferentially binds promoters of genes expressed before each moltSeveral identified genes have mammalian orthologues involved in rhythmic skin regeneration, implying a conserved process [ABSTRACT FROM AUTHOR]