In French, you would translate both "speed" and "velocity", by "vitesse". If you want to convey that velocity is a vector, you would say "vecteur-vitesse". Now, if you want to use the word "vélocité", as it is noted above, you speak about something different: "la vélocité de ce garçon de café est impressionnante" is a sentence that can be pronounced after a ...
(No native speaker; I teach in a French University).
As far as I know there is the noun vélocité but I don't encounter it very often (if at all).
Instead one would use vecteur vitesse if a distinction should be made between the norm (i.e. speed) and the vector (i.e. velocity).
One can verify it here