That's a very impressive blade ! I've found the same shape here :
http://www.africanarms.com/gallery?3-mbole-64-5-cm described as Mbole, however, the grip on your example is very different. What is it made of ? Bronze ? I also found this one, with a rather similar grip :
https://www.catawiki.com/l/7284189-a...bole-d-r-congo
As a disclaimer, though, I have absolutely no knowledge on weapons of this area, and as such can' tell you if that attribution is correct or not (still a starting point for your own research though, I guess).