The Joburg-based franchise announced on Monday that Venter will join them from Edinburgh in July 2026.
Venter has agreed to return to South Africa after six seasons in Scotland, where he established himself as one of the most reliable loosehead props in the Vodacom URC.
Venter made his Springbok debut in July, scoring a try in a commanding win over Georgia in Nelspruit. He went on to earn eight Test caps, featuring prominently in victories against Argentina in Durban, France in Paris and Ireland in Dublin.
The 28-year-old began his professional career with the Cheetahs before moving to Edinburgh in 2020, where he went on to make 94 appearances for the Scottish club.
Over that period, he developed into a durable and consistent front-row presence, earning a reputation for his high work rate, physicality and scrummaging stability.
Venter said it was not an easy decision to depart Edinburgh after six seasons, but he wanted to be closer to his family back home, while his blossoming Bok career no doubt played a major part as well.
"It was a tough decision to leave a club that has become home, but I am excited for the opportunity with the Emirates Lions and to be closer to family," said Venter.
"I want to thank all the Edinburgh fans for their incredible support over the years. I have enjoyed every moment of my time in this amazing city and wearing the jersey.
"I can assure everyone that I will be giving my absolute all for this badge and my teammates right up until the final whistle of the season."
Edinburgh head coach Sean Everitt said: "On behalf of everyone at Edinburgh Rugby, I would like to thank Boan for his services to the club over the past five years.
"He has been a big part of our squad and has certainly made an impact on the field, which was rewarded with his international call-up.
"We wish him and his family all the very best for his move back to South Africa and his new challenge with the Lions."