The smallest amphibian (and vertebrate) in the world is a microhylid frog from New Guinea (Paedophryne amauensis) first discovered in 2012.
ðə smˈɔːlɪst æmfˈɪbiən ænd vˈɜːɾɪbɹˌeɪt ɪnðə wˈɜːld ɪz ɐ mˈaɪkɹoʊhˌaɪlɪd fɹˈɑːɡ fɹʌm nˈuː ɡˈɪni pˈiːdəfɹˌaɪn ˌæməˈɛnsɪs fˈɜːst dɪskˈʌvɚd ɪn tˈuː θˈaʊzənd twˈɛlv.