Egyptian Rousette Bat Macrophage Colony-Stimulating Factor (M-CSF) is a cytokine that regulates the development, proliferation, and survival of monocytes and macrophages in the Egyptian rousette bat (Rousettus aegyptiacus). M-CSF is produced by a variety of cell types, including fibroblasts, endothelial cells, and stromal cells, in response to tissue signals and inflammatory stimuli. Egyptian rousette bat M-CSF binds to the colony-stimulating factor-1 receptor (CSF1R), a receptor tyrosine kinase expressed on monocytes and macrophage lineage cells, activating intracellular signaling pathways such as PI3K–AKT, ERK/MAPK, and JAK–STAT that promote differentiation and maintenance of macrophage populations. Through these mechanisms, M-CSF supports macrophage-mediated immune surveillance, tissue homeostasis, and inflammatory responses. In cell culture, recombinant Egyptian rousette bat M-CSF is commonly used to promote differentiation and survival of monocytes into macrophages and to support macrophage proliferation and functional studies in bat immune cell models. Egyptian rousette bats are natural reservoirs for several zoonotic viruses, including filoviruses such as Marburg virus, making M-CSF an important factor in research investigating bat macrophage biology and host–pathogen interactions that influence viral tolerance and immune regulation.