Bailieborough Castle, demolished country house site in Bailieborough, County Cavan, Ireland

Bailieborough Castle was a country house built by 1629 in an enclosed demesne southwest of Castle Lough, on the northwestern edge of Bailieborough. Also called Castle House, Lisgar House or The Castle, it was renovated by Sir John Young, 1st Baron Lisgar, before his death in 1876. Nothing of the building survives.

William Bailie received lands from James I in 1610 and built a fortified house, attracting Scottish families to settle in the area by 1629. The property underwent major changes during the following centuries as ownership and purposes shifted.

The estate held ties to Irish politics through several owners who served as Members of Parliament for County Cavan. These connections shaped the social standing and activities on the property over the centuries.

A single 3-kilometre (1.9 mi) loop, the Castle Lake loop, circles Castle Lake and enters Castle Lake Forest; it is suitable for walking or cycling and begins and ends at the car park on the lakeshore. The route passes the walled enclosure where several Marist Brothers are buried.

The Marist Brothers bought the house and 100 acres in 1915; after the 1918 fire they lived in a rebuilt section until 1936, then sold to the Department of Lands, and the house was demolished soon after. Several brothers are buried in a walled enclosure near the Castle Lake loop.