Mixed Hodge structures and representations of fundamental groups of algebraic varieties

Given a complex variety $X$, a linear algebraic group $G$ and a representation $\rho$ of the fundamental group $\pi \mathrm{\_}1(X,x)$ into $G$, we develop a framework for constructing a functorial mixed Hodge structure on the formal local ring of the representation variety of $\pi \mathrm{\_}1(X,x)$ into $G$ at $\rho$ using mixed Hodgediagrams and methods of $L\mathrm{\_}\mathrm{\infty }$ algebras. We apply it in two geometric situations: either when $X$ is compact K{"a}hler and $\rho$ is the monodromy of a variation of Hodge structure, or when $X$ is smooth quasi-projective and $\rho$ has finite image.