NOAA Ship Fairweather (S 220), originally operated by the United States Coast and Geodetic Survey as USC&GS Fairweather (MSS 20), is an oceanographic research ship operated by the National Oceanic and Atmospheric Administration (NOAA). Fairweather primarily conducts hydrographic surveys in Alaskan waters, but is considered a multi-mission-capable vessel and has conducted fisheries research cruises. She is the sister ship of the NOAAS Rainier (S 221) and of the retired NOAAS Mount Mitchell (S 222).