  Momentum and spatial distributions of quarks and gluons inside hadrons are
typically encoded in the so-called generalized parton distributions (GPDs).
GPDs are multi-dimensional quantities that are very challenging to extract,
both experimentally and within lattice QCD. We present the first lattice
results on the $x$-dependence of isovector unpolarized, helicity and
transversity GPDs of the proton, obtained from lattice QCD using an ensemble of
$N_f=2+1+1$ maximally twisted mass fermions, with pion mass $M_\pi=260$ MeV and
lattice spacing $a\simeq 0.093$ fm. Our calculations use the quasi-distribution
formalism and the final distributions are presented in the MS-bar scheme at a
renormalization scale of 2 GeV.
