Blood cancers are a highly diverse group of malignancies with over 150 distinct subtypes recognized by the World Health Organization (WHO) classification. Apart from a handful of common malignancies, individual subtypes are mostly rare and understudied from a genomics standpoint. The ABCG Project is a systematic clinical and genomic profiling of all 150+ WHO-recognized blood cancer types. We founded a consortium composed of 25 clinical institutions worldwide that collectively enrolled over 12,000 cases spanning all blood cancer entities. All cases were accompanied by complete, de-identified pathology data, allowing confirmation of diagnosis by a centralized pathology review board. Additionally, samples were accompanied by detailed clinical data including relevant clinical variables and survival outcomes. We performed whole exome and transcriptome sequencing to generate comprehensive genomic readouts encompassing genetic drivers, gene expression profiles, cell surface markers, copy number alterations, lymphocyte clonality and blood cancer-related pathogens. Importantly, standardized methods were applied across diagnoses, facilitating cross-disease comparisons that are unfeasible with existing piecemeal studies. The ABCG represents the largest and most comprehensive genomic and clinical dataset ever assembled for blood cancers. The results from the ABCG Project will be publicly available via a purpose-built online portal. We anticipate that this rich resource will drive discoveries that will improve disease treatment and therapy development in many ways for years to come.