  We extend our relativistic theory of electroweak properties of composite
systems to describe simultaneously the gravitational form factors of hadrons.
The approach is based on a version of the instant-form relativistic quantum
mechanics and makes use of the modified impulse approximation. We exploit the
general method of the relativistic invariant parametrizaton of local operators
to write the energy-momentum tensor of a particle with an arbitrary spin. We
use the obtained results to calculate the gravitational form factors of the
pion assuming point-like constituent quarks. All but one parameters of our
first-principle model were fixed previously in works on electromagnetic form
factors. The only free parameter, $D_{q}$, is a characteristic of the
gravitational form factor of a constituent quark. The derived form factors of
the pion satisfy the constraints given by the general principles of the quantum
field theory of hadron structure. The calculated gravitational form factors and
gravitational mean-square radius are in a reasonable agreement with known
results.
