An embedding theorem for the Orlicz-Sobolev space
$W^{1,A}_{0}(G)$, $G\subset \mathbb{R}^n$, into a space of
Orlicz-Lorentz type is established for any given Young function
$A$. Such a space is shown to be the best possible among all
rearrangement invariant spaces. A version of the theorem for
anisotropic spaces is also exhibited. In particular, our results
recover and provide a unified framework for various well-known
Sobolev type embeddings, including the classical inequalities for
the standard Sobolev space $W^{1,p}_{0}(G)$ by O'Neil and by
Peetre ($1\leq p< n$), and by Brezis-Wainger and by Hansson
($p=n$).