Constructor may refer to:

• Constructor (object-oriented programming), object-organizing method
• Constructor (video game), a 1997 PC game by Acclaim, the prequel of Constructor: Street Wars
• Constructors (Formula One), person or group who builds the chassis of a car in auto racing, especially Formula One
• Constructor (software), a software product by Graphisoft used to schedule and estimate buildings
• Constructor Group AS, a Norwegian-based group specialising in shelving, racking and storage systems
• An entity in Constructor theory, a theory of everything developed by physicist David Deutsch in 2012.

crt0 (also known as c0) is a set of execution startup routines linked into a C program that performs any initialization work required before calling the program's main function. It generally takes the form of an object file called crt0.o, often written in assembly language, which is automatically included by the linker into every executable file it builds.