Killiney Beach is located in South Dublin just South of Killiney Head. It is a long stoney beach that is about 4 kilometres long until it reaches Shankill Beach. The beach is very stoney and when the tide is fully out, there is a steep incline between low tide and the back of the beach. There is a railway line that runs along the back of the beach, so Dart Trains are a regular occurrence.
The railway line cuts the beach off from the coast road, but there is a large carpark located beside the Dart Station. You should park here and walk to the end of the carpark, furthest from the entrance. There is a pathway here that goes under the railway line to the beach. There is a coffee shop on the beach a couple of hundred metres to your left. In addition, are public toilets in the carpark that are well maintained by the local council.
Sat-Nav co-ordinates for the carpark are 53.256398, -6.113174 . There is a pay and display parking system in operation, so bring some coins with you!
As you are already in Killiney, consider a visit to Killiney Head, which overlooks the beach in places.