There is an ongoing genetic flow from the mitochondrial genome to the nuclear genome. The mitochondrial sequences that have integrated into the nuclear genome have been shown to be drivers of evolutionary processes and cancerous transformations. In addition to their fundamental biological importance, these sequences have significant consequences for genome assembly and phylogenetic and forensic analyses as well. Previously, our research group developed a computational pipeline that provides a uniform way of identifying these sequences in mammalian genomes. In this paper, we publish MANUDB-the MAmmalian NUclear mitochondrial sequences DataBase, which makes the results of our pipeline publicly accessible. With MANUDB one can retrieve and visualize mitochondrial genome fragments that have been integrated into the nuclear genome of mammalian species. Database URL: manudb.streamlit.app.