  V1765 Cyg is a detached eclipsing binary containing a B0.5 supergiant and a
B1 main-sequence star, with an orbital period of 13.37 d and an eccentricity of
0.315. The system shows apsidal motion and the supergiant exhibits strong
stochastic variability. V1765 Cyg was observed by the Transiting Exoplanet
Survey Satellite over four sectors. We analyse these data to obtain the first
determinate light curve model for the system. To this we add published
spectroscopic orbits to infer masses of 23 +/- 2 Msun and 11.9 +/- 0.7 Msun,
and radii of 20.6 +/- 0.8 Rsun and 6.2 +/- 0.3 Rsun. These properties are in
good agreement with theoretical predictions for a solar chemical composition
and an age around 7 Myr. We also present two epochs of blue-optical
spectroscopy that confirm the luminosity classification of the primary star and
appear to show absorption lines from the secondary star. Extensive spectroscopy
and further analysis of the system is recommended.
