Nechtan, Nectan or Neithon is an ancient Celtic name. It may refer to:

• An Irish water god, most often spelled Nechtan
• Saint Nectan, 5th/6th Century saint associated with Devon and Cornwall
• Nechtan I of the Picts, a 5th or 6th century King of the Picts
• Nechtan II of the Picts, a 7th century King of the Picts
• Neithon of Alt Clut, 7th century king of Alt Clut
• Nechtan IV of the Picts, an 8th century King of the Picts
• Nechtan of Aberdeen , 12th Century bishop of Aberdeen
• Nechtan Scéne, a character in the Ulster Cycle of Irish mythology