Plas Mawr is a historic house in Conwy, north Wales, dating from the 16th century. The house has been restored to its original appearance, with assistance from Cadw, in whose care it is now. It is thought to be the best-preserved Elizabethan town house in the United Kingdom.
The house was built between 1575 and 1586 for a merchant named Robert Wynne (or Wynn), who died in 1598, and is located near the centre of the town of Conwy. Wynne described the house as a "worthy, plentiful house". The ornamental plasterwork, which is the house’s most striking feature, carries the initials of its owner - "R W" - in several places. The gardens have also been restored by Cadw.
Robert Wynne was the 3rd son of John Wynne (ap Meredith), d.1553, and was uncle to Sir John Wynne of Gwydir through his brother Morys. Not being the first son, and therefore not inheriting on his father’s death, he travelled around Europe. He returned to Conwy, and married, but his first wife died a year after Plas Mawr was completed. Aged 66 he married Dorothy, and they had 7 children in the space of 6 years. In 1589 he became an MP for Caernarfon. Following his death there was fierce arguing over his inheritance, and finally Robert Wynne, his grandson, inherited in 1616.
Members of the Wynne family used to stay at Plas Mawr until moving to Gwydir, near Llanrwst, in 1564.