This dataset contains 474 drainage basin boundaries for U.S. Geological Survey (USGS) streamgages in Alaska, including supplemental drainage basin boundaries for alternate conditions for 3 of the 471 streamgages. The basin boundaries were delineated from the streamgage location to the nearest USGS Watershed Boundary Dataset (WBD) HUC boundary and along HUC boundaries from that intersection to the basin headwaters. The dataset also includes the streamgage locations used for delineation, which consist of points snapped from the streamgage coordinates in the USGS National Water Information System to the USGS National Hydrography Dataset flowline representing the respective streams. Streamgages selected for drainage basin delineation included: (1) streamgages having at least 10 years of peak-streamflow data through water year 2012, used for a statewide flood frequency study (Curran and others, 2016), and (2) streamgages in Cook Inlet Basin, regardless of record length, used for development of Cook Inlet Basin Streamstats in 2016 (https://streamstats.usgs.gov/ss/). For three streamgages, a supplemental drainage basin boundary was delineated for the drainage area associated with regulated (diverted) streamflow conditions contemporaneous with a period of streamflow record other than the present. Selected basins were previously published in the WBD as "NWISDrainageArea" features.