The　main　objective　of　this　paper　is　to　study　the　optimal　distributed　control　of　the　three-dimensional　planetary　geostrophic　equations.　We　apply　the　well-posedness　and　regularity　results　proved　in　Cao　and　Titi　(Commun　Pure　Appl　Math　56:198-233,　2003)　to　establish　the　existence　of　an　optimal　control　as　well　as　the　first-order　necessary　optimality　condition　for　an　associated　optimal　control　problem　in　which　a　distributed　control　is　applied　to　the　temperature.