A comprehensive understanding of nervous system function requires molecular insight into the diversity and sex dimorphism of both its component cell types, glia and neurons. Here, we present a single-nuclear RNA sequencing (RNA-seq) census of all neuroectoderm-derived glia in the adult C. elegans nervous system, across sexes. By iteratively coupling computational modeling and custom analytics with in vivo validations, we uncovered molecular markers for all glia, as well as class-specific and pan-glial molecular signatures. These identified that each glia is functionally heterogeneous across the nervous system and variably sex dimorphic between sexes. Thus, this glial transcriptome (wormglia.org) offers deep mechanistic insights into glial biology brain wide. Complementing the existing C. elegans neuronal transcriptome and mapped connectome, it also enables single-cell and molecular resolution insight into the entire nervous system of an adult metazoan.