This report provides insight into the main stratigraphic and sedimentary aspects of the Ordovician System in major tectonic units of Poland: (1) East European Craton, (2) Pomeranian Block, (3) Łysogóry Block, (4) Małopolska Block, (5) Upper Silesian Block, and (6) the Sudetes. The first studies of the Ordovician rocks in Poland were conducted as early as the second half of the nineteenth century in outcrops of the Holy Cross Mountains (SE Poland). Moreover, the Ordovician rocks are exposed in the Sudetes, where they are incorporated into the tectonostratigraphic units accreted during the Variscan orogeny. Significant progress has been made since the 1950s in the recognition of the Ordovician stratigraphic and facies architecture due to numerous drilling cores, which have been mostly made in NE Poland (East European Craton). The temporal and spatial facies pattern in the Polish part of the East European Craton indicate that in the Early and Middle Ordovician this area was a part of large, epicontinental carbonate platform replaced in the Late Ordovician by fine-grained clastics of distal shelf. The Ordovician sedimentary record in the Łysogóry and Małopolska blocks (SE Poland) reveals numerous similarities to the facies architecture in the neighbouring East European Craton, especially its marginal localities. Thus, it is possible to distinguish the same eustatic events in these units corresponding to sea-level changes reported in Baltica, although locally a regional tectonic activity masked their effects. The evolution of the sedimentary basin in NW Poland (Pomeranian Block) was influenced by the collision of Baltica with Avalonia in the Late Ordovician, which resulted in the development of the Caledonian fold-and-thrust belt.