Within the budding yeasts, the opportunistic pathogen Candida glabrata and other members of the Nakaseomyces clade have developed virulence traits independently from the CTG clade that includes Candida albicans. To begin exploring the genetic basis of C. glabrata virulence and its innate resistance to antifungals, we launched the Hermes transposon from a plasmid and obtained more than 500,000 different semi-random insertions throughout the genome.Using machine learning, we identify up to 1278 protein-encoding genes (25% of total) that cannot tolerate transposon insertions and are thus essential for C. glabrata fitness in vitro.Interestingly, genes involved in mRNA splicing were less likely to be essential in C. glabrata than their orthologs in S. cerevisiae, whereas the opposite is true for genes involved in kinetochore function and chromosome segregation. Insertions in several known genes (e.g. PDR1, CDR1, PDR16, PDR17, UPC2A, DAP1) caused hypersensitivity to the first-line antifungal fluconazole, and we identify 12 additional genes that also contribute to innate fluconazole resistance (KGD1, KGD2, YHR045W, etc). Insertions in 200 other genes conferred significant resistance to fluconazole, two-thirds of which function in mitochondria and likely down-regulate Pdr1 expression or function. These findings show the utility of transposon insertion profiling in genome-wide forward-genetic investigations of fungal pathogens. IMPORTANCE Pathogenic yeasts cause mucosal and systemic infections in millions of people each year. The innate resistance of Candida glabrata to fluconazole and its ability to acquire resistance to