You wrote in a comment to a now- deleted answer:
My visa expires in a month, and the purpose of the trip is to renew the visa at the US consulate in my home country, Ireland. My visa is tied to my Australian passport. I just want to make sure that if I leave the US on my Irish passport, that it will not be considered "overstaying" my US visa.
Since your Australian passport allows you to enter Ireland without a visa, I would suggest that you show the Australian passport to the airline at check-in, ensuring that your departure from the US is matched to your most recent entry. Then when you arrive in Ireland, show your Irish passport to enter the country.
As an aside, you may be interested to know, if you don't already, that you are not required to leave the US before the expiration date on your visa. The critical date is the one on your I-94, which is usually also written on your most recent admission stamp. If instead of showing a date it reads D/S then you can stay as long as you are eligible for your current immigration status.