Reconstruction maps and map sequences provide the essential basis and boundary conditions for interpreting ancient Earth system processes. Such maps can be generated using a variety of techniques to reunite formerly conjugate features as interpreted in a range of different data types. The highest confidence is achieved by reuniting large numbers of geographically widespread and precisely located markers that are simply and robustly interpreted. These markers are most widespread in the oceanic lithosphere, because of its relatively simple tectonic history of plate divergence that ends with subduction. The reliability of maps decreases with time in the past as the distribution of markers is first confined to the continental crust and, before this, to geographically ever-smaller and geologically more interpretation-dependent remnants, alongside which the range of suitable reconstruction techniques narrows. Relative reconstructions must be placed in a global reference frame, using any of a variety of techniques that also become smaller with past time. Reconstructions have been used for paleogeographic mapping to provide constraints on studies of regional deformation and to provide constraints on plate motion for geodynamic studies.