Abstract Background: Breast cancer is a global health challenge and the highest incident cancer globally, with over 2 million new cases and 685,000 deaths in 2020, making it the highest incident cancer globally. Furthermore, it is the most prevalent cancer, resulting in the loss of more disability-adjusted life years than any other malignancy. Research is thus crucial to improving outcomes and reducing suffering for breast cancer patients worldwide. This study aimed to analyse global patterns of funding for breast cancer research. Methods: We have previously created a comprehensive database of awards for human cancer research in this period using publicly available data on research funding awards. From this database we extracted all awards relating to breast cancer research, and categorised these by cancer type, cross-cutting research theme and phase of research. Findings: We identified 7051 awards with a total investment of $2.6 billion in 2016-2020, representing 11.2% of all global public and philanthropic cancer research funding during this period. Breast cancer research funding fell year on year, from $773.4 million in 2016 to $243.8 million in 2020. The majority of the investment was in pre-clinical research ($1.9 billion, 73.9%), with clinical trials ($276 million, 10.7%) and public health ($269.2 million, 10.5%) receiving roughly equivalent amounts of funding. The USA accounted for 66.9% of all global breast cancer research investment, with China ($110.4 million, 4.3%) and the UK ($96.6 million, 3.8%) the next largest funders. By research theme, cancer biology research received most funding ($926.2 million, 37.5% of investment), with drug treatment the next best funded research area ($600.5 million, 23.4%), and diagnosis, screening and monitoring third ($396 million, 15.4%). Surgery ($65.2 million, 2.5%) and radiotherapy ($35.3 million, 1.4%) accounted for only a small proportion of research investment. There was minimal investment into breast cancer as a global health issue ($8.1 million, 0.3%). Research into metastatic disease received a greater proportion of investment in breast cancer than in the overall cancer portfolio (23.2% in breast cancer, $597.4 million, compared with 11.7% across all cancers). Conclusions: Breast cancer public and philanthropic research funding is largely invested in pre-clinical research in high-income countries, with the main areas of investment being cancer biology research and drug treatment. The direct benefit to patients from such research is likely to be low and only apparent after a substantial time lag (if at all). Despite their pivotal role in the treatment of the majority of breast cancer patients, surgery and radiotherapy research received a tiny proportion of the overall research investment. Furthermore, relatively little investment is directed towards cancer prevention and early detection, despite their acknowledged key role in cancer control globally. Finally, more equitable research funding is required to align with the global burden of breast cancer, with increased funding for low- and middle-income countries, which account for an increasing proportion of this burden. These data should be considered by funders and policymakers in the allocation of finite resources, which must be invested wisely. Citation Format: Stuart McIntosh, Ellen Copson, Ramsey Cutress, Michael Head. The allocation of US $2.6 billion in global funding for breast cancer research between 2016 – 2020: are we investing wisely for breast cancer patients? [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO3-10-09.