Úna Bhán waltz
Also known as Una Bhan, Una Bhan,Oonagh Bhán,Oona Bhan,Oonagh Ban,Oona Ban,Una Ban.
There are 20 recordings of this tune.
Úna Bhán has been added to 8 tunebooks.
It’s really more of a slow air, and note lengths are quite arbitary, but I suppose you could theoretically play it as a waltz.
It’s doubtless based on a Sean-Nós song of the same name, but I’m sure someone will fill in the details below
Here’s an example of what it sounds like: https://www.youtube.com/watch?v=QiiZrUmF8HA