  We explore the moir\'e magnon bands in twisted bilayer magnets with
next-nearest neighboring Dzyaloshinskii-Moriya interactions, assuming that the
out-of-plane collinear magnetic order is preserved under weak interlayer
coupling. By calculating the magnonic band structures and the topological Chern
numbers for four representative cases, we find that (i) the valley moir\'e
bands are extremely flat over a wide range of continuous twist angles; (ii) the
topological Chern numbers of the lowest few flat bands vary significantly with
the twist angle; and (iii) the lowest few topological flat bands in bilayer
antiferromagnets entail nontrivial thermal spin transport in the transverse
direction; These properties make twisted bilayer magnets an ideal platform to
study the magnonic counterparts of moir\'e electrons, where the statistical
distinction between magnons and electrons leads to fundamentally new physical
behavior.
