  MEGARA is an optical integral field and multiobject fibre based spectrograph
for the 10.4m Gran Telescopio CANARIAS that offers medium to high spectral
resolutions (FWHM) of R $\simeq$ 6000, 12000, 20000. Commissioned at the
telescope in 2017, it started operation as a common-user instrument in 2018. We
are creating an instrument-oriented empirical spectral library from MEGARA-GTC
stars observations, MEGASTAR, crucial for the correct interpretation of MEGARA
data. This piece of work describes the content of the first release of
MEGASTAR, formed by the spectra of 414 stars observed with R $\simeq$ 20000 in
the spectral intervals from 6420 to 6790 $\r{A}$ and from 8370 to 8885 $\r{A}$,
and obtained with a continuum average signal to noise ratio around 260. We
describe the release sample, the observations, the data reduction procedure and
the MEGASTAR database. Additionally, we include in Appendix A, an atlas with
the complete set of 838 spectra of this first release of the MEGASTAR
catalogue.
