In　recent　decades,　the　advancement　of　clean　energy　technologies　and　sewage　purification　has　emerged　as　a　focal　point　of　research.　This　review　focuses　on　the　ammonia　oxidation　reaction　(AOR)　and　summarizes　its　multifaceted　applications,　including　its　use　in　direct　ammonia　fuel　cells　(DAFCs),　its　coupling　with　the　hydrogen　evolution　reaction　(HER),　and　its　significance　in　ammonia-containing　sewage　purification.　We　discuss　how　the　combination　of　in-situ　characterization　techniques　and　theoretical　models　has　emerged　as　a　powerful　tool　for　exploring　the　AOR　mechanism.　The　interplay　of　operational　parameters　such　as　temperature　and　pH,　along　with　catalyst　design,　is　emphasized　in　the　context　of　DAFCs,　highlighting　the　need　for　precise　optimization　to　enhance　efficiency.　The　importance　of　selectivity　in　the　nitrogen　gas　product　in　ammonia-containing　wastewater　is　also　discussed.　Furthermore,　the　review　addresses　the　challenges　and　opportunities　in　AOR　research,　including　strategies　to　enhance　catalytic　activity,　identify　active　centers,　maximize　the　utilization　of　catalyst　atoms,　and　improve　selectivity　while　ensuring　catalyst　durability.　Ultimately,　this　review　serves　as　a　comprehensive　guide　for　researchers　and　practitioners　interested　in　harnessing　the　potential　of　AOR　to　bridge　the　gap　between　clean　energy　generation　and　sustainable　wastewater　treatment,　offering　insights　into　a　greener　and　more　environmentally　responsible　future.　(c)　2023,　Dalian　Institute　of　Chemical　Physics,　Chinese　Academy　of　Sciences.　Published　by　Elsevier　B.V.　All　rights　reserved.