Dependency injection (DI) is a programming design pattern and architectural model, sometimes also referred to as "inversion of control" or "IoC", although technically speaking dependency injection specifically refers to an implementation of a particular form of IoC. The pattern seeks to establish a level of abstraction via a public interface, and to remove dependency on components by (for example) supplying a plug-in architecture. The architecture unites the components rather than the components linking themselves or being linked together. Dependency injection is a pattern in which responsibility for object creation and object linking is removed from the objects themselves and transferred to a factory. Dependency injection therefore is obviously inverting the control for object creation and linking, and can be seen to be a form of IoC.

There are three common forms of dependency injection: setter, constructor and interface based injection.

Some examples of implementations of dependency injection include the Spring framework for Java, and Ruby on Rails for the Ruby programming language.