The Greenland Ice Sheet (GrIS) is the second largest ice mass on Earth, covering approximately 20% of Arctic land surface area. As rising global temperatures increase annual melting of the GrIS, it is increasingly important to determine the ability of ice melt to transport nutrients and contaminants to nearby oceans where they can impact marine ecosystems. Manganese (Mn) is a trace element and essential micronutrient that can limit phytoplankton growth, and it therefore plays an important role for ecosystem health. Despite its biological importance, observational data on Mn concentrations and reactivity in the cryosphere is limited, and the role of the GrIS in the Mn biogeochemical cycle remains largely unknown. Here, I compare spatial and temporal Mn trends in GrIS meltwaters to assess the hypothesis that glacially derived Mn is a critical micronutrient source for coastal marine ecosystems. Suspended sediments were collected daily between early June-late July from the Watson River (southwestern Greenland) in 2023 and the Kiattuut Sermiat meltwater river (southern Greenland) in 2024. Mn was extracted from the sediments using sequential extractions, and Mn concentrations were analyzed by Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). Concentrations of total Mn in glacial meltwater rivers are several orders of magnitude higher than in a nearby precipitation-fed stream, indicating that glacially derived sediment may be the dominant source of particulate Mn exported from GrIS catchments. The dominant pool of Mn is highly reactive across the entire melt season in both sampled meltwater rivers, but the specific composition of particulate Mn varies between different glacial catchments. I conclude that GrIS meltwaters overall may be a significant source of highly reactive Mn to coastal environments, but that local geological and hydrological characteristics cause variation in Mn composition between catchments. To my knowledge, this study provides the first dataset of particulate Mn in GrIS meltwaters, addressing a significant gap in current understandings of Mn inputs from glacial environments.