How many types of design patterns are?

Gang of Four Design Patterns

List of the Original 23 Patterns PurposeDesign PatternAspect(s) that can varyStructuralCompositestructure and composition of an objectDecoratorresponsibilities of an object without subclassingFacadeinterface to a subsystemFlyweightstorage costs of objectsDesign Patterns cs.lmu.edu › ~ray › notes › designpatterns

As per the design pattern reference book Design Patterns – Elements of Reusable Object-Oriented Software , there are 23 design patterns which can be classified in three categories: Creational, Structural and Behavioral patterns.