The B4556 is a short B-road in south Carmarthenshire. Originally unclassified, it gained its number in 1935.
The road starts on the A476 in Gorslas, only a short distance northeast of the A48, and heads east through town along Penygroes Road. We merge almost seamlessly into that village, where we are crossed by the B4297. On entering open country for the first time we detour to the north from the old road, which was destroyed by opencast mining, then returns to its original route to pass through Blaenau. There's then another detour, this time to the east; the stubs of the old road are still visible this time at either end of the diversion.
We return to the old route on the edge of Llandybie and head north into town along Blaenau Road. It's not long before journey's end at a T-junction on the A483.