Biomass is a highly versatile renewable energy source used on a global scale. The paper discusses the current state of biomass energy use in the EU and Slovakia. Residual biomass was found as a key feedstock for the European bioeconomy. Slovakia is one of the most forested and rural countries in the EU. Therefore, biomass energy has the highest technical potential from all renewables in Slovakia. The main objective of the paper was to evaluate the phytomass production of the selected crops and their energy potential in individual self-governing regions of Slovakia. It is focused on the production of usable post-harvest residues theoretically used for energy purposes from the following studied main crops: wheat, rye, oats, barley, maize, potatoes, oilseed rape and sugar beet. The results show the estimated production of usable post-harvest residues of the selected crops and their energy potential in individual self-governing regions in Slovakia in 2019. The total production of usable post-harvest residues from the studied crops was 4,854,017 t and their estimated energy potential was 68 PJ. This amount of energy would cover 10% of the total energy consumption in Slovakia. The top three productive crops were maize, wheat, and sugar beet. Maize had the highest energy potential of 28.1 PJ, followed by wheat at 19 PJ and sugar beet at 14.2 PJ. The highest yields of post-harvest residues, as well as energy potential, were found in the Nitra region.