The Snowdonia Society (Welsh: Cymdeithas Eryri) is a members based environmental charity. Formed in 1967 by Esmé Kirby, it is concerned with all aspects of the Snowdonia National Park. Members take part in practical activities to improve the environment and engage in campaigns to prevent inappropriate development in the area. The Society also organises a lecture programme, publishes books and magazines, maintains a detailed website, runs themed walks and organises competitions to preserve crafts such as dry stone walling. Membership is open to all with an interest in Snowdonia and can be obtained via the Society's website.
The Society owns Tŷ Hyll (English: The Ugly House), which is located on the A5 between Betws-y-coed and Capel Curig. This house is reputed to be a "tŷ unnos", i.e. it was built overnight in order to establish legal ownership. Tŷ Hyll and its gardens are open to the public, and until 2011 housed the Society's offices. A teashop now occupies the ground floor. The policies of the Society are decided by its elected executive committee. The Society's paid staff support the charity's honorary officers and manage projects in areas such as waste reduction, energy efficiency and practical conservation.
The Society also maintains a public database of people who have completed the Welsh 3000s