Clareen (Irish: An Cláirín, meaning 'little plain')[1] is a village in the parish of Seir Kieran in County Offaly, Ireland.

It is the location of a Church of Ireland church (built in 1840 in the grounds of the Monastic site), a Roman Catholic church (built in 1901 on the south-eastern slope of Bell Hill), the Seir Kieran National School (built in 1874), and the Seir Kieran GAA Club (founded in 1887).

Clareen was the site of an early Christian monastery known as Seir Kieran, in honour of its founder, Saint Ciaran of Saigir.

The monastery is one of the oldest Christian settlements in Ireland dating from the 5th century.

[2] All that remains of the early monastery are the stump of a round tower and the base of a high cross.