ABSTRACT In this paper, we present and validate the galaxy sample used for analysis of baryon acoustic oscillation (BAO) signal in Dark Energy Survey (DES) Y3 data. The definition is based on a colour redshift-dependent magnitude cut optimized to select galaxies at redshifts higher than 0.5, while ensuring high-quality determination. covers ${\sim }\, 4100$ deg2to depth i = 22.3 (AB) 10?. It co...