Late 17th century burial ground set an in idyllic location on a man-made promontory to Loch Katrine. From 1859 Loch Katrine became used as Glasgow's main source of drinking water functioning as a reservoir, as a result the water level of the loch was artificially raised. In 1922 to avoid the burial site being submerged the Glasgow Corporation raised it up onto a T-shaped causeway allowing access from the heightened shoreline to the burial ground. The site is one of the historical burial grounds of the MacGregor's of Glengyle. The legendary Rob Roy MacGregor was born at nearby Glengyle in 1671. He is not buried at this site, instead resting in the burial ground of The Old Parish Church at Balquhidder.
The burial site is located to the far SW end of the causeway, a retaining wall runs to the SW, NW and SE raising the site some height above the water level. The site is enclosed by a wall running to the NE which links it with the retaining wall. It is swept up at the entrance with an inscribed lintel. The lintel is badly weathered but is believed to bear the MacGregor of Glengyle crest and the motto 'E'en do and spare not' and the inscription 'In regard of the memory of her dear husband, Malcolm MacGregor, and their worthy son, John MacGregor, this chapel ws repaired by Katherine MacGregor of Glengyle, 1781'. A low wall within the site encloses 12 grave slabs, the earliest appears to date from 1699. A further 4 slabs lie outwith the low wall to the NW of the site.
Formerly listed as Macgregor of Glengyle burial ground, Portnellan, Loch Katrine. The Clan Gregor became established in Glengyle in the earlier 17th century and later expanded in strength into Balquhidder, Glen Orchy, Breadalbane and Rannoch. The clans expansion was curtailed by the government in 1611 when they were prosecuted by Act of Privy Council. The MacGregors retained their house and land at Glengyle. It is thought that for a time Rob Roy MacGregor lived at a dwelling near the burial ground at Portnellan. The burial ground appears to have ceased being used in the early 19th century. Another MacGregor burial ground founded in the 18th centuryis located to the W of nearby Glengyle House. The Glengyle Estate was purchased by Glasgow Corporation in 1918.