Llanfaes is a small village on the island of Anglesey, Wales, located on the shore of the eastern entrance to the Menai Strait, the tidal waterway separating Anglesey from the north Wales coast. Its natural harbour made it an important medieval port and it was briefly the capital of the kingdom of Gwynedd. Following Prince Madoc's Rebellion, Edward I removed the Welsh population from the town and rebuilt the port a mile to the south at Beaumaris. It is in the community of Beaumaris.

Joan, Lady of Wales and Lady of Snowdon, also known by her Welsh name often written as Siwan was the illegitimate daughter of King John of England, and was the wife of Llywelyn the Great, Prince of Wales, effective ruler of all of Wales. Joan or Siwan in Welsh has been referred to as both "Lady of Wales" and "Princess of Wales".