The former SuperSport United striker has penned a three-year deal with Sundowns, with the move confirmed last night.
The Senegalese forward had also attracted interest from Orlando Pirates, Bidvest Wits and Bloemfontein Celtic.
“It's a new chapter for me and it is a new challenge something I have been looking forward to it,” Niang said.
“I enjoyed my years at SuperSport, it's a great club they looked after me well and everything went well.
“I'm joining the team to Cape Town tomorrow (today). I have signed a three-year-deal and one option.”
Niang said the reason he chose Downs over their rivals was based on his desire to challenge himself, that and the prospect of playing Champions League football.
“Pitso phoned me while I was in Europe and told me that he wants me to join Sundowns. I had other options but I felt Sundowns was the real challenge for me,” he continued.
“I didn't think twice I just took the chance and I said yes I will like to join them.
“There was Bidvest Wits, there was Pirates, Celtic even wanted me so I opted for the big one and the challenging one. So I felt Sundowns was the challenging one.
“Sundowns is a winning team and I am looking forward to add something different to the team. They got so much quality and I'm hoping I can profit in that and I'm just looking forward to play with the quality players there and score some goals and win some silverware hopefully everything will go well.”