A real matrix is called “Totally Positive” if all of its entries, minors, and determinant are positive. Lustig’s notion of total positivity generalises this to any split real semi simple Lie group and plays and important role in representation theory. I will talk about a recent generalisation of total positivity to non-split real semi simple Lie groups called Theta-Positivity due to Guichard and Wienhard, and about how noncommutative cluster algebras can encode this kind of positivity.