Breachacha Castle is either of two structures on the shore of Loch Breachacha, on the Inner Hebridean island of Coll, Scotland. The earlier is a 15th-century tower house that was a stronghold of the Macleans of Coll, the island having been granted to John Maclean in 1431. This castle was superseded by a new dwelling in 1750 (see below) but continued to be occupied for a time, falling into a ruinous state only in the mid-19th century. Although work was performed in the 1930s to prevent further dilapidation, the castle was restored to livable condition only in the 1960s, by Major N. V. MacLean Bristol. It is a Category A listed building.
The newer Breachacha Castle (also known as Breachacha House), which is also a Category A listed building, was constructed in the mid-18th century 140m northwest of the old castle . It was in this house that Samuel Johnson and James Boswell stayed on their tour of the Hebrides.