The aim of the study is to evaluate the content of organic carbon (Corg) in the soils of Polish grasslands (GL). The Tiurin's method (mineral soils) and the mass loss method (soil of organic origin) were used. It was found that: /i/ the average Corg content of mineral soils is 2.44% and of organic soils – 10.42%; /ii/ according to the Polish criteria, about 84% of GL mineral soils are classified as classes with high and very high Corg content, and over 15% and 1% – in classes with medium and low Corg content, respectively; more than 99% of organic soils belong to two classes with the highest Corg content and less than 1% to the class with an average content; /iii/ according to the European Soil Bureau, the share of GL mineral soils with a high Corg content is slightly over 4%, medium – slightly over 47%, and low and very low – around 50%; for organic soils they are 67%, 29%, and 4%, respectively; /iv/ the reserves of organic carbon in the 0–30 cm layer on the entire surface of GL soils amount to 412.7 million tons of Corg. There are opportunities to increase the Corg stock in meadow soils.