Gels are attracting materials for a range of applications [1, 2]. In particular, gels containing water (namely, hydrogel) or exhibiting stability under bio-relevant conditions have been finding fruitful biorelated applications [3]. The latest decade has been witnessed a rapid growth in research on gels exploring, for instance, polymer gels (chemical gels) with bio-orthogonal cross-linking and hydrogels (mostly physical gels) composed of biomolecules such as short peptides, proteins, (poly)saccharides, and nucleic acids.

In this special issue, to cover a wide range of research topic concerning such gels, we organized team composed of the editor-in-chief, an associate editor, and guest editors. We collected 10 Original Articles, 1 Note, 3 Focus Reviews, and 4 Reviews from (young) outstanding researchers from Japan, Korea, Germany, Portugal, USA, and Australia, which can provide the readers with an overview of this rapidly growing research field. Also, we would like to leave “biofunctional gels” not strictly defined and it to the authors as well as the readers, which may facilitate discussion or imagination to find their future applications.

Since 2012, Polymer Journal has published special issues on the related topics, e.g., self-assembled materials [4, 5], peptide materials [6], and biorelated materials [7]. As with recent special issues [8,9,10,11,12,13,14,15], we hope that this special issue is also valuable for the contemporary readers of this journal. Last, but certainly not least, we sincerely appreciate all authors and referees for their contribution to this issue.