Pol an Ionain, Show cave in County Clare, Ireland

Poll an Ionain is a limestone cave near Doolin, County Clare, on the western edge of the Burren. Its entrance is a low opening in a grassy hillside, framed by a grey limestone lintel on stacked stone blocks and closed by a black metal gate of vertical bars. Inside, a 45-minute guided tour leads to the Great Stalactite, a free-hanging stalactite reported at 7.3 m long, though lengths of 6.2 m, 6.54 m and 11 m have also been given.

J. M. Dickenson and Brian M. Varley of the Craven Pothole Club, an English caving club, discovered the cave in 1952 after a long, difficult crawl. In 1990 John and Helen Browne bought the land and developed it as a show cave. The Speleological Union of Ireland objected to a planned 30-metre blasted shaft; no blasting was used, and the cave opened in 2006. A visitor centre and café followed in 2010.

The Irish name Poll an Eidhneáin is anglicised as Poll an Ionain and is said to mean "Ivy Cliff Cave". The cave sits near Doolin on the western edge of The Burren, and the show cave is now marketed simply as Doolin Cave. Its development as a visitor attraction in the early 21st century drew controversy, and it has twice received Gold Standard from Ecotourism Ireland, in 2013 and 2015.

The cave maintains a constant temperature around 11°C year-round, so warm and weather-appropriate clothing is necessary for comfort. Visitors should wear sturdy shoes with good grip to move safely on wet and uneven surfaces during the tour.

The Great Stalactite is a free-hanging formation reported at 7.3 m long, though sources also give 6.2 m, 6.54 m and 11 m. It is the longest known free-hanging stalactite in Europe; the three longer ones are in two Mexican caves and Jeita Grotto in Lebanon.