There are following below 11 Design Patterns supported by Magento 2
[1] Object Manager Design Pattern
[2] Dependency Injection Design Pattern
[3] Factory Design Pattern
[4] Proxy Design Pattern
[5] Preferences Design Pattern
[6] Argument Replacement Design Pattern
[7] Virtual Types Design Pattern
[8] Events and observers Design Pattern
[9] Plugins Design Pattern
[10] Repository Design Pattern
[11] Injectable/Non-Injectable Object