  We present a complete dynamical study of the intermediate polar and dwarf
nova cataclysmic variable GK Per (Nova Persei 1901) based on a multi-site
optical spectroscopy and $R$-band photometry campaign. The radial velocity
curve of the evolved donor star has a semi-amplitude $K_2=126.4 \pm 0.9 \,
\mathrm{km}\,\mathrm{s}^{-1}$ and an orbital period $P=1.996872 \pm 0.000009 \,
\mathrm{d}$. We refine the projected rotational velocity of the donor star to
$v_\mathrm{rot} \sin i = 52 \pm 2 \, \mathrm{km}\,\mathrm{s}^{-1}$ which,
together with $K_2$, provides a donor star to white dwarf mass ratio
$q=M_2/M_1=0.38 \pm 0.03$. We also determine the orbital inclination of the
system by modelling the phase-folded ellipsoidal light curve and obtain
$i=67^{\circ} \pm 5^{\circ}$. The resulting dynamical masses are
$M_{1}=1.03^{+0.16}_{-0.11} \, \mathrm{M}_{\odot}$ and $M_2 =
0.39^{+0.07}_{-0.06} \, \mathrm{M}_{\odot}$ at $68$ per cent confidence level.
The white dwarf dynamical mass is compared with estimates obtained by modelling
the decline light curve of the $1901$ nova event and X-ray spectroscopy. The
best matching mass estimates come from the nova light curve models and an X-ray
data analysis that uses the ratio between the Alfv\'en radius in quiescence and
during dwarf nova outburst.

Solar and Stellar Astrophysics