The Artognou stone, sometimes referred to as the Arthur stone, is an archaeological artefact uncovered in Cornwall in the United Kingdom. It was discovered in 1998 in securely dated sixth-century contexts among the ruins at Tintagel Castle in Cornwall, a secular, high status settlement of sub-Roman Britain. It appears to have originally been a practice dedication stone for some building or other public structure, but it was broken in two and re-used as part of a drain when the original structure was destroyed. Upon its discovery the stone achieved some notoriety due to the suggestion that "Artognou" was connected to the legendary King Arthur, though scholars such as John Koch have criticized the evidence for this connection.