The　integration　of　polymer　networks　of　dissimilar　chemistries,　such　as　hydrogels　and　hydrophobic　elastomers,　has　enabled　numerous　existing　and　emerging　applications　in　engineering　and　medicine.　However,　it　remains　a　challenge　to　adhere　polymer　networks　of　dissimilar　chemistries　when　neither　network　contains　functional　groups　for　chemical　coupling.　Here　we　describe　a　principle　of　dual-primer　adhesion　that　meets　this　challenge.　For　each　preformed　network,　we　formulate　a　primer　with　uncrosslinked　polymers　that　(1)　match　the　chemistry　of　the　preformed　network,　and　(2)　contain　coupling　agents　for　crosslinks　and　interlinks.　We　apply　the　primer　on　the　surface　of　the　preformed　network,　place　two　primed　networks　in　contact,　and　cure.　Each　primer　crosslinks　into　a　network,　in　topological　entanglement　with　the　one　preformed　network,　and　the　two　primer　networks　form　interlinks.　The　stitch-bond-stitch　topology　covalently　adheres　the　two　preformed　networks.　We　demonstrate　the　principle　by　using　polydimethylsiloxane　elastomer,　polyacrylamide　hydrogel,　and　silane　coupling　agents.　Adhesion　energy　as　high　as　∼140　J/m2　is　achieved,　comparable　to　the　toughness　of　the　polyacrylamide　hydrogel.　The　principle　of　dual-primer　adhesion　opens　an　enormous　design　space　for　general　applications.　©　2020