  Raman lasers is an actively developing field of nonlinear optics aiming to
create efficient frequency converters and various optical sensors. Due to the
growing importance of ultracompact chip-scale technologies, there is a constant
demand for optical devices miniaturization, however, the development of a
nanoscale Raman laser remains a challenging endeavor. In this work, we propose
a fully subwavelength Raman laser operating in visible range based on a gallium
phosphide nanocylinder resonator supporting a quasi bound state in the
continuum (quasi-BIC). We perform precise spectral matching of nanoparticle's
high-$Q$ modes with the pump and detuned Raman emission wavelengths. As a
result of our simulations, we demonstrate a design of Raman nanolaser, ready
for experimental realization, with the lasing threshold expected to be as low
as $P_{\mathrm{th}} \approx 21~\mathrm{mW}$. The suggested configuration, to
the best of our knowledge, represents the very first prototype of a
low-threshold Raman nanolaser with all the dimensions smaller than the
operational wavelength.
