The Stormers signed the Cape Town native off the back of playing for the SA U20 side back in 2022 and he has cemented his place in the star-studded squad.
Hartzenberg, who turned 22 on Tuesday, was instrumental in the Stormers' 34-24 win over Cardiff in the United Rugby Championship match on Saturday. The winger celebrated his 50th cap in style, scoring two tries, topping the ball carry stats and earning the Man of the Match accolade.
"In my first year, it was more about finding my feet and getting used to the system and understanding what they want from me," reflected Hartzenberg.
"As the years went on now, I think I found myself a bit more and understood what is expected from me by the coaches and from the team.
"It is just about performing at my best.
"Having guys like Damian Willemse, Dan du Plessis, Sacha Feinberg-Mngomezulu, and Manie Libbok makes my job easier. We are all on the same page."
Hartzenberg has been involved in several Springbok alignment camps and Stormers boss John Dobson is backing his player to wear the green and gold soon.
"This guy was special," said Dobson.
"It's incredible. It was his 50th, and he is only 21, and to play like he played, we are super proud. He is just super.
"He can play for South Africa at wing or centre. He is going to, I've got no doubt."