WWE’s Spanish Twitter account revealed that the winner of the 50-man Greatest Royal Rumble match will receive a trophy as the prize.
11 DÍAS para el Mayor #RoyalRumble de todos los tiempos.
— WWE Español (@wweespanol) April 16, 2018
It was originally rumored that the winner of the match may receive a future world title match but that doesn’t appear to be the case. WWE could always add that as a stipulation at a later date.