The longest river is the Dnieper, the longest tributary is the Dnieper's tributary Desna. Two of the Danube's tributaries in Ukraine, the Prut and the Tysa, are longer than the main river within Ukraine.
The Dnieper River is the longest river, while its tributary, the Desna, is the longest tributary. Two of the Danube's tributaries in Ukraine, the Prut and the Tysa, surpass the length of the main river within Ukraine.