Hydrogels are physically or chemically cross-linked polymer networks that are able to absorb large amounts of water. They can be classified into different categories depending on various parameters including the preparation method, the charge, and the mechanical and structural characteristics. The present review aims to give an overview of hydrogels based on natural polymers and their various applications in the field of tissue engineering. In a first part, relevant parameters describing different hydrogel properties and the strategies applied to finetune these characteristics will be described. In a second part, an important class of biopolymers that possess thermosensitive properties (UCST or LCST behavior) will be discussed. Another part of the review will be devoted to the application of cryogels. Finally, the most relevant biopolymer-based hydrogel systems, the different methods of preparation, as well as an in depth overview of the applications in the field of tissue engineering will be given.