Getting to Olympia by  public transport is common for backpackers as it is very cheap but  we do recommend you avoid this means of transport if you have children, lots of luggage, or lose your temper easily.
For both train and bus your ticket will get you to Pyrgos. You then  need to get off the bus/train and purchase a ticket for the  remainder of the trip (20km) which also means you will have to wait for approximately 20 minutes.
 

Train

Trains and buses take a  considerable (usually) amount of time to get to their destinations. If your starting point is Athens the details you need are:

By train you have to ask for a ticket to Pyrgos. The train travels the route Athens-Patras-Pyrgos.
Your starting station will be: "Stathmos Peloponnisou" which means Peloponnese station.
If you want more information please call (0030) 1110 or click the following link: More train information

Bus

If you want to travel  by bus then you need to get to Kifissou street 100 (else called "Stathmos Kifissou") were the bus terminals are. There you can catch a ride to anywhere in mainland Greece. You need to ask for a ticket to Pyrgos.  The bus travels the same route as the train which is no other that via Patras.
The phone number of the Kifissos station is 210-5134110 / 210-5124910.
More bus Information