Nyungwe is in the far southwest corner of Rwanda. The drive from Kigali is around six hours on a paved road — south through Huye (formerly Butare), then west through Nyamagabe and on into the forest. Public minibuses run as far as Huye and then to Cyangugu on the western edge of the park; private hire is more practical if you're stopping to walk.
The main road, the RN1, runs straight through the park between Uwinka and Gisakura. Driving through is scenic in itself — long stretches of unbroken forest canopy on either side, with the occasional troop of monkeys crossing in front of the car. Allow time: the road is winding, and stops for wildlife are common.