Plas Newydd is a country house set in gardens, parkland and surrounding woodland on the north bank of the Menai Strait, in Llanddaniel Fab, near Llanfairpwllgwyngyll, Anglesey, Wales. The current building has its origins in 1470, and evolved over the centuries to become one of Anglesey's principal residences. Owned successively by Griffiths, Baylys and Pagets, it became the country seat of the Marquesses of Anglesey, and the core of a large agricultural estate. The house and grounds, with views over the strait and Snowdonia, are open to the public, having been owned by the National Trust since 1976.

Llanfairpwllgwyngyll or Llanfair Pwllgwyngyll, sometimes shortened to Llanfair PG, is a village and community on the Isle of Anglesey, Wales. It is located on the Menai Strait, next to the Britannia Bridge. At the 2011 Census the population was 3,107, of whom 71% could speak Welsh. In 2021, the population decreased to 2,900. It is the sixth largest settlement in the county by population.