The paper is focused оті the specificity of the hydronym Labe in Czech toponymicai system, investigating especially its role in derivation of toponyms (most often anoikonyms), but also its occurrence in prepositional and multiple-word names. It becomes obvious that the use of this hydronym in creation of toponyms differs substantially from other bydronyms, whose use is very limited. The toponyms referring to other rivers most often derive horn the common nouns řeka ‘river’ or -voda ‘water’ (prdy rarely from the particular hydronym), whereas these common nouns never refer to the river Labe in Czech toponymy. Furthermore, some affixes used for deriving toponyms from the hydronym Labe are otherwise not used for the creation of toponyms from toponymical bases. These finding result into the conclusion that the hydronym Labe functions similarly to a common noun in the Czech toponymical system.