Lleolir Rhoshirwaun tua 3km i'r gogledd ddwyrain o Aberdaron ar y B4413. Y mae'r pentref wedi ei wasgaru ar rosdir ddeheuol Llyn.

I gyfeiriad Aberdaron ar yr ochor dde y mae mynydd Ystym gydag olion Castell odo ar ei gopa.

Rhoshirwaun is situated about 3 Km North East of Aberdaron along the B4413. The village is scattered across the inland Southern plateau of Llyn.

Towards Aberdaron is the hill of Mynydd Ystym with the remains of Castell odo, an early settlement.