Pirates chairman Irvin Khoza revealed the Bucs captain’s departure at a press conference on Thursday.
“Oupa Manyisa will be joining Sundowns. He has an unbelievable record with Pirates,” said Khoza.
“Oupa Manyisa leaves to Sundowns as a highly decorated Orlando Pirates player.
“It is not an easy decision but in the best interest of the player. There are still a few details to finalize.”
Manyisa has had a hard time living up to expectations after being named the captain of Pirates.
He is said to have failed to unite the dressing with reports coming out of Pirates saying there were different camps inside the club.