The initialism SAD may refer to:

• Schizoaffective disorder, a psychiatric diagnosis
• Social anxiety disorder
• Seasonal affective disorder, typically winter depression
• Separation anxiety disorder

• Shiromani Akali Dal, a political party in India
• Special Activities Division of the US Central Intelligence Agency, now named the Special Activities Center
• Saraya Awliya al-Dam, an Iraqi militia

• Sociedad Anónima Deportiva, a type of incorporated sports club in Spain
• Sociedade Anónima Desportiva, a type of incorporated sports club in Portugal

• Selected area diffraction, a crystallographic experimental technique
• Sum of absolute differences, in digital image processing
• Single-wavelength anomalous dispersion, in X-ray crystallography

• Sandwell & Dudley railway station, with the station code SAD
• Safford Regional Airport, Arizona, US, with the IATA airport code SAD

• "S.A.D.", by Man Overboard from Heart Attack (2013)
• "Sad!", by XXXTENTACION (2018)

• SAD scheme, a form of intellectual property enforcement in the United States
• Singles Awareness Day, a humorous holiday every February 14
• The Single Administrative Document, EU customs form
• The Standard American Diet, another name for the Western pattern diet
• The Suicide Attack Database, now named the Database on Suicide Attacks
• Sagittal abdominal diameter, body diameter at the waistline

• Sad (disambiguation)