The large Portal Tomb of Cloonlooaun (in Irish, Cluain Luáin) is situated on the southern slope of a rocky hill, approximately 3.0 kilometers south of Renvyle, west of Clifden (in Irish, An Clochan) in Connemara, County Galway, Ireland.

The Portal Tomb is located on a leveled platform of about 10.0 meters in diameter on the hill. Portal Tombs are megalithic structures found in the British Isles, characterized by two equally tall, upright stones with a doorstone in between, forming the front of a chamber covered, in part, by a massive capstone.

The Portal Tomb consists of two upright stones, approximately 1.8 meters and 1.6 meters high, with a doorstone of about 1.2 meters in height in between. The chamber, which is about 2.3 meters long and 1.4 meters wide, has two preserved sidewalls in the southwest. The northwest sidewalls have collapsed into the interior of the chamber and cover the ground. The large flat stone to the west is the displaced capstone, measuring 2.4 meters by 1.55 meters and 0.20 meters thick.

Adjacent to the capstone is an enclosure that appears to be made from the material of the cairn.

Approximately 1.0 kilometer to the north lies the Wedge Tomb of Ardnagreevagh, and to the west, the Court Tomb of Tonadooravaun.