The chemical composition of lakes is an important ecosystem property that can have considerable influence on aquatic ecosystem structure and function. Since lake chemistry is sensitive to climate and disturbance, lakes may serve as a sentinel of current and projected [SDM1] climate change through long-term monitoring. Here, we report findings from a two-year pilot study aimed at characterizing the chemical composition of large lakes in National Park Service lands of the Arctic Inventory and Monitoring Network (ARCN). We collected water samples from 20 large lakes in Bering Land Bridge National Preserve (BELA), Gates of the Arctic National Park (GAAR), and Noatak National Preserve (NOAT) during the 2013 and 2014 field seasons (between June and September). Water samples were analyzed for dissolved organic matter (DOM) composition, nutrient concentrations, major cations and anions, and water stable isotopes. We also collected field measurements of lake surface temperature and temperature profiles, specific conductivity, and pH. We observed considerable variation in the chemical composition of large lakes with ARCN parks. For instance, DOC concentrations ranged from 1 to 12 mgC L-1 across all lakes, and DOM aromaticity was highly variable, as indicated by measurements of specific ultraviolet absorbance (SUVA254). Nutrient concentrations (nitrogen and phosphorus species) were generally low, indicating oligotrophic conditions and likely strong nutrient-limitation of primary production. Cation and anion concentrations varied across lakes, reflecting spatial variations in lithology. Overall, large lakes appear to be unimpaired with respect to a broad suite of water quality parameters. However, Arctic lakes are likely vulnerable to climate-driven changes hydrology and landscape disturbance (e.g. wildfire and permafrost thaw). Future monitoring of large lakes ARCN should be designed to detect chemical and hydrologic properties across space and time, both as a means of assessing these vulnerabilities and for improving watershed management activities.