Auchenbreck Castle (also spelt Auchinbreck) is located in Argyll and Bute, Scotland.

Its remains are situated in Kilmodan parish, near the south of Glendaruel, 9 kilometres (5.6 mi) north of Tighnabruaich on the Cowal peninsula.

Around 1703 the castle was purchased by John Fullarton, former minister of Kilmodan, and later Bishop of Edinburgh.

Fullarton renamed the estate Greenhall, and was the last person to live in the castle.

When the estate was sold in 1728, after Fullarton's death, it included a mansion which may have been built from the stones of the castle.