Neutrophils, the most prevalent and efficient immune responders to pathogens, play vital roles in tumor progression and metastasis. Sustained neutrophil infiltration into tumor has been consistently linked to unfavorable clinical outcomes. Despite recent advances, critical knowledge gaps persist concerning the heterogeneity of neutrophils in the tumor microenvironment and throughout carcinogenesis and the reliable marker sets that define protumoral neutrophil subsets. Here, we constructed a comprehensive pan-cancer single-cell transcriptomic atlas of human neutrophils across 12 types of cancer, and revealed substantial heterogeneity among neutrophils. Notably, we identified CD83 as a hallmark of tumor-associated neutrophils (TANs) and found that CD83+ neutrophils are significantly enriched in cancerous tissues during carcinogenesis. Furthermore, CD83+ TANs represented a more senescent state, as confirmed by both bioinformatics analysis and the detection of SA-β-galactosidase activity. Additionally, CD83+ senescent TANs could regulate an immunosuppressive microenvironment by suppressing the activation and cytotoxicity of T cells; and their abundance exhibited significant association with poor prognosis and immunotherapy resistance. Finally, a therapeutic strategy, HDAC inhibitor romidepsin, was explored for its potential of specifically eliminating CD83+ senescent protumoral TANs. In summary, our study underscores the association between CD83+ senescent protumoral TANs and poorer clinical outcomes, offering novel perspectives on neutrophil-based therapeutic and prognostic approaches.© 2025 The Authors. Published by Elsevier B.V. on behalf of Research Network of Computational and Structural Biotechnology.