Hydrogels are widely used in biomedical fields including drug delivery due to their unique properties such as biocompatibility, biodegradability, flexibility, and non-toxicity. Because of their advanced properties, the interest in hydrogels is increasing day by day. Although re-searchers have been working on developing new hydrogels and enhancing the properties of the existing ones, there are still many remaining unsolved challenges for the improvement. This review paper handles the topic of hydrogels as drug delivery systems (DDS). Herein, we summarize the properties, advantages, classification, and preparation methods of hydrogels. We highlighted some recent progress of hydrogels as unique drug delivery vehicles. The future perspective of the use of them were eventually enlightened.