In response to increasing food demand and limited natural resources, agriculture is seeking alternative feed sources for livestock. Grapevine (Vitis vinifera) leaves, a by-product of the wine industry, represent a promising option. This study compared the chemical composition of leaves from four grape cultivars (‘Regent’, ‘Rondo’, ‘Seyval Blanc’, ‘Solaris’) and assessed their potential as livestock feed. Research was conducted at the Nobilis vineyard in the Sandomierska Upland. Biometric parameters and quality traits were analysed, including leaf area, leaf mass, leaf number per shoot, lignified shoots per bush, and contents of moisture, protein, fibre, ash, NDF, ADF, ADL, organic matter, dry matter digestibility, total sugars, and related measures. Significant cultivar differences were observed. ‘Solaris’ showed the greatest leaf area and mass, suggesting higher feedstock potential. ‘Seyval Blanc’ had the smallest leaves but the highest leaf number per shoot and per hectare. ‘Rondo’ and ‘Regent’ were distinguished by high protein content and digestibility, and ‘Regent’ had the highest soluble sugar content. The findings indicate that vine leaves could reduce winery waste, support sustainable agriculture, and improve livestock feed quality.