Many marine organisms including foraminifera are geographically dispersed in the World Oceans depending on paleo-oceanographic conditions. Due to its oceanographical conditions, many foraminiferal species represented by different families are dispersed from the littoral to the deep basins of the Sea of Marmara. Most of them originated from the Mediterranean Sea. The Sea of Marmara, formed as a result of the paleogeographic evolution of the region, is an isolated sea between the Black Sea and the Aegean Sea with different oceanographic characteristics because of the density differences of both connected seas. This feature makes the Sea of Marmara important among the world's seas. The different and sudden deep basins, which reach a depth of more than 1000 meters depending on the geological history of the Sea of Marmara, show different physical and chemical properties. Numerous species that adapt to these varying conditions also form the biological diversity of these environments. Of these, an important group is the foraminiferal community. This group is extremely diverse and is represented by different taxa distributed in the shelf and deep environments of the Sea of Marmara. The surveys that have been made up to date show that every new study has brought the addition of new taxa to the known biological diversity of the Sea of Marmara. Research carried out within the scope of the MAREM project yields 28 (26 benthic and 2 pelagic) new records added to the foraminiferal fauna of the Sea of Marmara. With the new records in the present study, the total number of known foraminifera species has increased from 309 to 337 in the Sea of Marmara. (C) 2019 Elsevier Masson SAS. All rights reserved.