  We classify principal $2$-blocks of finite groups $G$ with Sylow
$2$-subgroups isomorphic to a wreathed $2$-group $C_{2^n}\wr C_2$ with $n\geq
2$ up to Morita equivalence and up to splendid Morita equivalence. As a
consequence, we obtain that Puig's Finiteness Conjecture holds for such blocks.
Furthermore, we obtain a classification of such groups modulo $O_{2'}(G)$,
which is a pure group theoretical result and of independent interest. Methods
previously applied to blocks of tame representation type are used. They are,
however, further developed in order to deal with blocks of wild representation
type.
