Do you need to have an international driver's permit in Greece?

Yes

Since the IDP is an official translation of your American license, and Greek is very different from English, I think it would be foolish to go without. Whether it is a requirement for renting a car, ask your rental company.

According to www.autoeurope.com, the answer is "yes."

Greece is not the place to be if a police officer decides you have been naughty

A car rental agency will probably not bother to ask you for it, but if a policeman does and you don't have it you're in deep doo-doo. Also, if you get in a wreck and don't have it there's a very good chance your car rental insurance will be invalidated because you didn't comply with the law.

Greek may be very different from English, but if you look inside that IDP there is NO Greek translation of your American license. I'm not saying that you don't need one, since rental agencies vouchers clearly state that one is mandatory, but...it's not logical that its purpose is to translate, yet it doesn't translate!

And since when does "logic" have anything to do with travel in Greece?

We rented a car from the Athens airport (Avis) and the agent requested to see DH's IDL. I'm not sure if she would have refused to rent the car if he had not had one, but I'm supposing she was asking for a good reason... not out of idle curiousity.
If you live near a AAA shop, you can get one in about 5 minutes for less than $20

I know, I know...I already got mine because it was printed in black & white on the rental voucher. But it bugs me to have to "play by the rules" when it's so illogical. That Greek policeman that stops me will not be able to flip to a page of Greek language that translates my license into his/her language. And it wasn't $20, it was $28 to include the picture.

The IDL may not contain a Greek translation, BUT most police would be familar with what a legitimate IDL looks like. The IDL also has your photo pasted inside.

In case of accident, the IDL may also facilitate reaching your emergency contacts.

I got my IDP at AAA for $15 US. I printed my own photos on my printer.

Search: AAA Heathrow IDP.

No, I don't need an IDP/IDL for Greece, but maybe you do? I believe it depends on your nationality.

As long as the IDP has an Egyptian translation (demonic or hieroglyphic) you'll be ok in Greece. Just bring along a copy of the Rosetta stone too.

Non-EU citizens require an IDP for Greece - even if there isn't a Greek translation.

If the law required logic, we wouldn't have income tax regulations that fill one shelf of a bookcase.