Caernarfonshire ( Welsh: Sir Gaernarfon ), also Caernarvonshire or Carnarvonshire is one of the thirteen traditional counties and a former administrative county of Wales. Historical capital and the eponymous place is the town of Caernarfon.
The county is in the northwest of Wales by the sea and adjacent land side of Denbighshire and Merionethshire. The Isle of Anglesey is preceded Caernarfonshire. The landscape is characterized by the Snowdonia National Park with the Snowdon, the highest mountain in Wales. The north-west is occupied by the Lleyn Peninsula. The eastern boundary is formed by the River Conwy. Significant places besides Caernarfon are Bangor, Betws -y -Coed, Conwy, Llandudno, Porthmadog and Pwllheli.
1961 the county had 121 194 inhabitants in 1473 km ².
Until 1974 Caernarfonshire was an administrative county and was then divided among the three Districts Aberconwy, Arfon Dwyfor and the newly formed county of Gwynedd. Since the administrative reform of 1996, the area of the county is divided among the unitary authorities of Gwynedd and Conwy.