D50, D-50 or D 50 may refer to:

• CIE Standard Illuminant D50, a lighting standard used in colorimetry, and also in graphic design as a white point
• D50, in particle size distribution measurements, the mass-median-diameter, considered to be the average particle size by mass.
• D50 (radiotherapy), the half maximal inhibitory dose, representing the dose of light or ionising radiation that is required for 50% inactivation of a tumor cell population
• D50 road (Croatia), a state route
• Dodge D50, a compact pickup truck marketed by Chrysler and based on the Mitsubishi Triton
• the ICD-10 code for iron deficiency anemia
• An intravenous sugar solution of 50% dextrose
• Invisible D50, a keyboard stand
• JNR Class D50, a pre-war Japanese steam locomotives class related to the D60 steam locomotive class
• Lancia D50, a Formula One racing car driven by Juan Manuel Fangio to win the 1956 World Driver's Championship
• New South Wales D50 class locomotive, a NSWGR steam locomotive
• Nikon D50, an entry-level digital SLR camera
• Roland D-50, a digital synthesizer
• D50 (film), working title for a Tamil-language film