Most rental agencies will list it on their website when you make a booking, for example if I look at a coming one I have from Hertz in Mexico it clearly specifies:
At time of rental, the renter must present a valid driver's licence issued from country of residence. An International Driver's Licence is suggested, but not required.
Since I am using a Dutch driving license I can also go to the anwb website which for example tells me that my license is not valid in Egypt without an IDP, and if I try to make a booking at Hertz it also clearly states that
At the time of rental the driver must present a valid national driver's licence, which has been held for at least 1 year.
A valid International Driving Permit (IDP) is required for all renters.
The IDP translates the national licence into various languages and is on its own, without the national licence, not acceptable.