The River Trothy (Welsh: Afon Troddi) is a river which flows through north Monmouthshire, in rural south east Wales. The river rises on Campston Hill, northeast of Abergavenny. It flows southwards until Llanvapley, where it turns east. At Monmouth the river joins into the River Wye, about 0.5 km downstream from the mouth of the River Monnow.