The Lewis chessmen (Norwegian: Lewisbrikkene; Scottish Gaelic: Fir-Tàilisg; Scots: Lewis chesmen) or Uig chessmen, named after the island or the bay where they were found, are a group of distinctive 12th-century chess pieces, along with other game pieces, most of which are carved from walrus ivory. Discovered in 1831 on Lewis in the Outer Hebrides of Scotland, they may constitute some of the few complete, surviving medieval chess sets, although it is not clear if a set as originally made can be assembled from the pieces. When found, the hoard contained 93 artifacts: 78 chess pieces, 14 tablemen and one belt buckle. Today, 82 pieces are owned and usually exhibited by the British Museum in London, and the remaining 11 are at the National Museum of Scotland in Edinburgh.

Additionally, a newly identified piece, a "warder", the equivalent of a castle or rook, was sold for £735,000 in July 2019. Four other major pieces, and many pawns, remain missing from the chess sets.