Objective: The aim of this scoping review is to extract and describe the milk oligosaccharide composition of mammalian species and to investigate the similarities and differences between species in relation to the maturity of the newborn. Introduction: There is a growing interest in milk oligosaccharides because of their numerous benefits for newborn and long-term health. Since their discovery in 1930, a large number of structures has been identified in mammalian milks. Data for non-human species are less abundant but seems to indicate species-specific profiles of milk oligosaccharides. However, as of today, this information is scattered in several publications and not easily findable. A crucial step in understanding the functions of milk oligosaccharides is to characterise the structure of milk oligosaccharides among mammalian species. Inclusion criteria: This scoping review will include studies analysing the composition of oligosaccharides in the milk of mammalian species. We will only consider studies in English language but irrespective of geographic location or time frame. Methods: The JBI approach for conduct and reporting of scoping reviews will guide this review process. A preliminary search will be performed on Web of Science, followed by an analysis of titles, abstracts and keywords to refine the search query and extend the search to a second database, PubMed. Two independent reviewers will screen titles, abstracts and full texts of articles based on the inclusion criteria. Relevant studies will be reported in a draft extraction table.