Markov　decision　processes　(MDPs)　in　queues　and　networks　have　been　an　interesting　topic　in　many　practical　areas　since　the　1960s.　This　paper　Provides　a　detailed　overview　on　this　topic　and　tracks　the　evolution　of　many　basic　results.　Also,　this　paper　summarizes　several　interesting　directions　in　the　future　research.　We　hope　that　this　overview　can　shed　light　to　MDPs　in　queues　and　networks,　and　also　to　their　extensive　applications　in　various　practical　areas.　©　Springer　Nature　Singapore　Pte　Ltd　2019.