Rural Irish public transport is still relatively limited, as such it is advisable to book all journeys at least a day in advance to ensure there is space. The train should be booked further in advance as the price can fluctuate.
From Cork Airport / Cork City Centre
A regular bus service goes from outside Cork Airport to Parnell Place bus station in the city centre. From there you can either travel on Bus Eireann route 236 directly from Parnell Place, or with West Cork Connect from St Patricks Quay (a short walk across the river).
From Dublin Airport / Dublin City Centre
The most direct route from Dublin Airport is to get an Aircoach or Citylink bus from outside the airport departures direct to Cork and then follow the steps above to get from Cork City to Bantry. You can also get a bus into the city centre and then take the train from Heuston Train Station to Cork City. To travel directly from Dublin, you can get an Aircoach or Citylink bus from the city centre to Cork or the train from Heuston Station.
From Kenmare / Skibbereen
There is now a Bus Eireann route that travels from Kenmare, Kerry, to Skibbereen, Cork, via Bantry.