LDR may refer to:

• Light Dependent Resistor, an electronic component, also known as Photo-Resistor.
• Land Disposal Restrictions under RCRA
• Lateral Digit Reduction, a concept in paleontology to explain the wing formation in birds ; see origin of birds#Digit homology
• Laval-des-Rapides, a borough in Laval, Quebec, Canada
• Lecture and Dissertation Room, another name for a lecture hall
• Lift-to-drag ratio
• Long-distance relationship
• Low dynamic range rendering, a term used in 3D rendering
• .ldr, a file extension for the 3D Lego modeling LDraw tools
• LD-R, laserdisc abbreviation
• LDR, Geography Less Developed Regions
• Labor and Delivery Room, rooms in hospitals where women give birth
• Lana Del Rey, an American indie singer-songwriter.

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LDraw is a popular system of free software tools for modeling Lego creations in 3D on a computer. The LDraw file format and original program were written by James Jessiman. He also modeled many of the original parts in the parts library that is central to the programs and is under continuous maintenance and extension by the LDraw community. In 1997, Jessiman died. Since then, a variety of programs have been written that use the LDraw parts library, and file format. LDraw models are frequently rendered in POV-Ray, a free 3D ray tracer.