abstract: Motivated by Mostow's proof of Mostow rigidity, Tukia proved landmark results about when a group of quasi-conformal mappings of $\mathbb{R}n$ is quasiconformally conjugate to a conformal action. Gromov later pointed out that Tukia's theorem had fairly immediate consequences for the quasi-isometric rigidity of fundamental groups of hyperbolic manifolds. In these talks we will discuss recent generalizations of Tukia's theorem to a broader class of spaces, namely what we call Carnot-by-Carnot groups. The motivation for studying this class of spaces (and even broader ones) also comes from the study of quasi-isometric rigidity for certain groups and spaces. This work is joint with Xie.