The 24-year-old forward, a product of the franchise's academy who made his senior debut in 2021, has committed his long-term future to Pretoria.
Standing 1.99m and weighing 111kg, Ludwig has developed into one of the Bulls' most promising young locks.
He captained Afrikaanse Seuns Hoërskool's first XV and was head boy at the school before progressing through the Bulls system and earning SA U20 honours in 2021 and 2022.
"I would like to express my sincere gratitude and appreciation to the Bulls for the opportunity to extend," he said.
"It means a lot that the coaches and the management have shown their trust and belief in me.
"I'm really excited; they've built an unbelievable squad and it's such a privilege to be a part of that and I'm fully committed to giving my absolute best, working hard and doing everything I can to contribute to the success of this team to take the Bulls to another level in the next couple of seasons."
Blue Bulls Company CEO Edgar Rathbone praised the lock's qualities and the importance of retaining him: "Reinhardt is exactly the kind of player we want to build this team around.
"He has come through our system, he leads by example, and he has the athleticism and talent to become a mainstay in our starting side. Securing him until 2030 shows how much we believe in him and in the future of this squad."
Ludwig has already shown leadership credentials at senior level and continues to push for a regular starting role in a competitive engine room.