  In this work we prove that, given a simplicial graph $\Gamma$ and a family
$\mathcal{G}$ of linear groups over a domain $R$, the graph product
$\Gamma\mathcal{G}$ is linear over $R[\underline t]$, where $\underline t$ is a
tuple of finitely many linearly independent variables. As a consequence we
obtain that any graph product of finitely many groups linear over the complex
numbers is again a linear group over the complex numbers. This solves an open
problem of Hsu and Wise in the case of faithful representations over $\mathbb
C$.
