Hydrogels　are　crosslinked　hydrophilic　polymers　that　can　absorb　a　large　amount　of　water.　By　their　hydrophilic,　biocompatible　and　highly　tunable　nature,　hydrogels　can　be　tailored　for　applications　in　bioanalysis　and　biomedicine.　Of　particular　interest　are　DNA-based　hydrogels　owing　to　the　unique　features　of　nucleic　acids.　Since　the　discovery　of　the　DNA　double　helical　structure,　interest　in　DNA　has　expanded　beyond　its　genetic　role　to　applications　in　nanotechnology　and　materials　science.　In　particular,　DNA-based　hydrogels　present　such　remarkable　features　as　stability,　flexibility,　precise　programmability,　stimuli-responsive　DNA　conformations,　facile　synthesis　and　modification.　Moreover,　functional　nucleic　acids　(FNAs)　have　allowed　the　construction　of　hydrogels　based　on　aptamers,　DNAzymes,　i-motif　nanostructures,　siRNAs　and　CpG　oligodeoxynucleotides　to　provide　additional　molecular　recognition,　catalytic　activities　and　therapeutic　potential,　making　them　key　players　in　biological　analysis　and　biomedical　applications.　To　date,　a　variety　of　applications　have　been　demonstrated　with　FNA-based　hydrogels,　including　biosensing,　environmental　analysis,　controlled　drug　release,　cell　adhesion　and　targeted　cancer　therapy.　In　this　review,　we　focus　on　advances　in　the　development　of　FNA-based　hydrogels,　which　have　fully　incorporated　both　the　unique　features　of　FNAs　and　DNA-based　hydrogels.　We　first　introduce　different　strategies　for　constructing　DNA-based　hydrogels.　Subsequently,　various　types　of　FNAs　and　the　most　recent　developments　of　FNA-based　hydrogels　for　bioanalytical　and　biomedical　applications　are　described　with　some　selected　examples.　Finally,　the　review　provides　an　insight　into　the　remaining　challenges　and　future　perspectives　of　FNA-based　hydrogels.　©　The　Royal　Society　of　Chemistry　2016.