Edinburgh sells more ghost tours than almost any city in Europe, and the quality swings wildly, from serious underground history to a bloke in a cape jumping out from behind a bin. This is my pick of the ones worth your money, ranked, with the concept, the exact price, how frightening it really is, and who each suits. The short version: if you want genuine history under the Royal Mile, book the Real Mary King's Close or Mercat's Blair Street Vaults; if you actually want to be scared, the tour to take is City of the Dead into the locked Covenanters' Prison; and if you're bringing children, the Witchery walk or the Ghost Bus keep the tone light.
The honest thing to say first is that Edinburgh's single best underground experience isn't really a ghost tour at all. The Real Mary King's Close is a history tour through buried 17th-century streets, and it's superb, but nobody is going to leap out at you. Once you accept that, the field splits cleanly. Some tours are history-led: lit closes, plague, body-snatchers, a guide who knows their stuff. Others are scare-led: dark vaults, actors, jump scares, and in one case a graveyard poltergeist. Neither is better, they're just different nights out, and the mistake people make is booking one when they wanted the other.
Two practical notes before you go. Prices run from about £16 to £30 a head, most tours are 60 to 90 minutes, and the small-group ones sell out in summer and around Halloween, so book ahead. And check the age limits: the tamest of these welcome five-year-olds, but City of the Dead won't take under-12s and Auld Reekie's Terror Tour is adults-only for a reason. If you only do one and you're not chasing a fright, make it the Real Mary King's Close. If you are, make it City of the Dead.