Sag or SAG may refer to:

• sag (geology)
• any form of sagging
• a sag pond
• a lens sag (shape distortion)
• the SAG - Securitag Assembly Group, RFID Transponder Solution in Taiwan.(SAG RFID)
• an abbreviation relating to the astronomical Sagittarius (constellation) and astrological Sagittarius, as in Sagittarius Dwarf Irregular Galaxy (Sag DIG)
• Sag Harbor, New York
• Sâg, a commune in Sălaj County, Romania
• Şag, a commune in Timiş County, Romania
• the Screen Actors Guild (SAG)
• electric current, as in Voltage sag
• the plant Khada sag
• the culinary dish sa(ag) ghoust
• Semi-Autogenous Grinding, a technique used in milling
• an abbreviation referring to a Socially Awkward Guy or Socially Awkward Girl
• SQL Access Group (see ODBC)
• Songs About Girls music album by will.i.am.
• an acronym for Support And Gear or Support Aid Group used in Bicycling