Breccia ( or ) is a rock composed of broken fragments of minerals or rock cemented together by a fine-grained matrix that can be similar to or different from the composition of the fragments.
The word has its origins in the Italian language, in which it means "rubble". A breccia may have a variety of different origins, as indicated by the named types including sedimentary breccia, tectonic breccia, igneous breccia, impact breccia, and hydrothermal breccia.
A megabreccia is a breccia composed of very large rock fragments, sometimes kilometers across, which can be formed by landslides, impact events, or caldera collapse.