The short answer
The Castlemap atlas maps 297 landmarks in Japan: 165 castles, 3 fortresses, 11 palaces & châteaux and 118 ruins — each with a photo, its story and a page of its own.
Wikidata, the open database this atlas is built from, holds 2,449 items in Japan that are a castle, fortress, fort, château, palace, citadel or fortification of any kind — from a royal residence to a single surviving tower.
Figures published elsewhere often run higher still, because they count vanished sites and every surviving fragment of wall.
What a published source says
about 5,000 castles built at one time or another · 12 original keeps still standing — the Wikipedia article “Japanese castle”.
Why the numbers differ
What counts as a castle. A hilltop ruin, a fortified manor, a Baroque palace and a 19th-century folly are all “castles” in ordinary speech, and every count draws that line somewhere different.
Standing or vanished. Most fortifications ever raised are gone. A count of sites is a multiple of a count of buildings you can walk into.
Who did the counting. A national heritage register, an enthusiast’s database and an open dataset each stop at a different threshold of evidence.
What this atlas counts
247 of the 297 carry a sourced founding date. They run from 400 BC to 1909.
See them all on the map of castles in Japan →