Northern Water Snake 
Northern Western Ghats vine snake 
Northwestern garter snake 
Oligodon everetti 
Olive Forest Racer 
Olive House Snake 
Olive Keelback 
Olive Mountain Keelback 
Olive Trapezoid Snake 
Oliver's Parrot Snake 
Orange-collared keelback 
Orange-lipped Keelback 
Oriental ratsnake 
Oriental Whipsnake 
Oriental wolf snake 
Ornate Cat-eyed Snake 
Ornate flying snake 
Ornate Snail-eating Snake 
Oxyrhopus guibei 
Painted Bronzeback 
Palmer's snail-eater 
Papua New Guinea Montane Keelback 
Paradise flying snake 
Parrot snake