The main theorem of this paper is that 1-quasiconformal maps are smooth in all Carnot groups. This theorem can be used to prove rigidity theorems for quasiconformal maps between open subsets in certain classes of groups without any a priori smoothness assumption. For instance, the authors show that if \(G\) is a two-step Carnot group whose only dilation-preserving automorphisms are dilations, then the only quasiconformal maps between open subsets of \(G\) are translations composed with dilations. Combining the main theorem with the results in \textit{H. M. Reimann} [Math. Z. 237, 697--725 (2001; Zbl 0982.22013 )], the authors show a local version of one of the main results in \textit{P. Pansu} [Ann. Math. (2) 129, 1--60 (1989; Zbl 0678.53042)]. Suppose that \(G\) is the nilpotent group in the Iwasawa decomposition of the isometry group of the quaternionic or Cayley hyperbolic space. Then quasiconformal maps between two open subsets of \(G\) form a finite-dimensional subset of the space of smooth, generalized contact maps. Two more of the contributions of this paper should be highlighted. 1) The metric definition and Pansu's definition of 1-quasiconformal maps are equivalent, 2) The morphism property of 1-quasiconformal maps needs no extra regularity assumptions, i.e., if \(f\) is a 1-quasiconformal map defined on an open subset of a Carnot group \(G\), then composition with \(f\) preserves \(Q\)-harmonic functions.