  Due to the gravitational lensing effect, a black hole casts a shadow larger
than its horizon over a bright background, and the shape and size can be
calculated. The Event Horizon Telescope collaboration has produced the first
direct image (shadow) of the black hole and it is in accordance with the shadow
of a Kerr black hole of general relativity. However, deviations from the Kerr
black hole arising from modified theories of gravity are not ruled out and they
are important as they offer an arena to test these theories through
astrophysical observation. This stimulates us to investigate rotating black
holes surrounded by anisotropic fluid in Rastall theory namely a rotating
Rastall black hole, which is characterized by mass $M$, spin $a$, field
structure parameter $N_s$ and the Rastall parameter $\psi$. It encompasses, as
special cases, Kerr ($N_s \to 0$) and Kerr-Newman ($s=0$ and $N_s = -Q^2 $)
black holes. The rotating Rastall black hole is characterized by an additional
cosmological-like horizon apart from Cauchy and event horizons. We derive an
analytical formula for the shadow of a rotating Rastall black hole and go on to
visualize the shadow of black holes for various values of the parameters for an
observer at a given coordinate ($r_O, \theta_O$) in the domain $[r_+,r_q]$.
