Modern day Arabia is know as

After the defeating of Ottoman Empire in the WWI, the Saudis expanded their territories and took also the cities of Mecca and Medina, so, we can consider Saudi Arabia as "modern Arabia".

Explanation:

The Romans named three regions with the prefix "Arabia", encompassing a larger area than the current term "Arabian Peninsula": Arabia Petraea: for the area that is today southern modern Syria, Jordan, the Sinai Peninsula and northwestern Saudi Arabia.

middle east