Cercospora beticola, causal agent of Cercospora leaf spot of sugarbeet ( Beta vulgaris subsp. vulgaris), is the most economically damaging foliar pathogen inhibiting sugarbeet production. Despite the global importance of C. beticola, significant knowledge gaps exist pertaining to pathogen virulence and adaptation to management practices that include the use of resistant host varieties and the application of different fungicide chemistries. The lack of a high-quality reference genome for C. beticola has hindered research progression addressing these critical knowledge gaps. Here, we report the complete and gapless genome assembly and annotation of the reference C. beticola isolate Cb09-40. We identified misassembled regions in the previous reference genome and annotated previously missing protein-coding genes. This work establishes a high-quality reference genome that can serve as the foundation for future comparative genomic, population genetic, and evolutionary studies into the virulence and evolution of this important plant pathogen. [Formula: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .