Lyonesse is a country in Arthurian legend.
Lyonesse or Lyoness may also refer to:
Lyonesse, an Arthurian character; see Lynette and Lyonesse The Lyonesse Trilogy, a high fantasy trilogy by Jack Vance Lyonesse (novel), the first book of the trilogy Lyonesse, a fictional planet in the Foundation (book series) by Isaac Asimov Lyonesse, a fictional underground kingdom of Deviants in Marvel Comics SS Lyonesse, a ship built in 1889 for the ferry service between Penzance and the Isles of Scilly
See also Lyoness, a shopping community Lyonnaise (disambiguation)