Kudus came close to joining Everton last summer but Ajax blocked the move and made sure he stayed put in Amsterdam.
His reputation has only enhanced since that failed move, with him scoring 18 times in all competitions this season.
The attacker is expected to be courted by big clubs in the summer and Real Madrid are amongst the ones who are watching him.
It has been claimed that the Spanish giants sent scouts to watch Kudus in action for Ajax against Heerenveen on Sunday.
The forward had a huge impact on a game where he scored once and laid on an assist in a 4-2 win for Ajax.
Real Madrid scouts watched the player in action as he continued his form for the Dutch champions this season.
Kudus is also on the radar of Erik ten Hag, who is considering taking him to Manchester United in the summer.
He still has two years left on his contract but Ajax are expected to find it hard to hold on to him in the next window.