"Aisteoir."

Translation: An actor.

[wombatua]

So this is gender-neutral?

[scilling]

Yes. “Actress” could be translated as ban-aisteoir.

[Cathal42]

That is only if you want to make a point of her gender though. These days, gender-specific forms like that (eg banaltra, bangharda) have gone out of fashion

[zzxj]

Is banaltra gender specific, though? Teanglann.ie says a male nurse is banaltra fir, and there's no entry for altra.

[Knocksedan]

The body responsible for maintaining the register of Nurses is Bord Altranais agus Cnáimhseachais na hÉireann, "Nursing and Midwifery Board of Ireland".

The use of ban as a gender specific prefix is pretty much defunct now in job titles - the rank of bangharda was officially abolished in 1990, though the prefix ban still forms the function that the suffix "ess" forms in English, if you need to use it.

[Cathal42]

It's a change that's happened since Ó Dónaill's dictionary (which that site uses) was published. The New English-Irish Dictionary has altra http://www.focloir.ie/ga/dictionary/ei/nurse

[galaxyrocker]

Looking through usage examples, yes, it seems to be gender neutral. However, you can explicitly say actress, if you choose.