SD40 may refer to:

• Canon PowerShot SD40, a digital camera
• EMD SD40, a diesel-electric locomotive
• South Dakota Highway 40
• SD-40 alcohol, ethanol denatured by adding denatonium benzoate

• Archives department of Seine-Maritime
• Archives départementales de Seine-Maritime
• Archive Series No. 1: Live in Iceland
• Archives for London
• Archives fédérales suisses
• Archives in china
• Archives in the People's Republic of China
• Archives Journals
• Archives nationales
• Archives nationales du Sénégal
• Archives-Navy Mem'l-Penn Quarter (Washington Metro)
• Archives-Navy Memorial-Penn Quarter
• Archives - Navy Memorial - Penn Quarter (WMATA station)
• Archives Neerlandaises de Zoologie
• Archives Neerlandaises du Zoologie
• Archives of American Art
• Archives of Anthropos
• Archives of Asian Art
• Archives of asian art
• Archives of biochemistry and biophysics
• Archives of Biochemistry and Biophysics
• Archives Of Biochemistry And Biophysics
• Archives of Canada
• Archives of Computational Methods in Engineering
• Archives of disease in childhood