As part of the Chandra Galactic Bulge Survey (GBS), we present a catalogue of optical sources in the GBS footprint. This consists of two regions centered at Galactic latitude b=1.5{deg} above and below the Galactic Centre, spanning (lxb)=(6{deg}x1{deg}). The catalogue consists of 2 or more epochs of observations for each line of sight in r', i' and H{alpha} filters. The catalogue is complete down to r'=20.2 and i'=19.2mag; the mean 5{sigma} depth is r'=22.5 and i'=21.1mag. The mean root-mean-square residuals of the astrometric solutions is 0.04-arcsec. We cross-correlate this optical catalogue with the 1640 unique X-ray sources detected in Chandra observations of the GBS area, and nd candidate optical counterparts to 1480 X-ray sources. We use a false alarm probability analysis to estimate the contamination by interlopers, and expect ~10 0 per cent of optical counterparts to be chance alignments. To determine the most likely counterpart for each X-ray source, we compute the likelihood ratio for all optical sources within the 4{sigma} X-ray error circle. This analysis yields 1480 potential counterparts (~90 per cent of the sample). 584 counterparts have saturated photometry (r'<=17, i'<=16), indicating these objects are likely foreground sources and the real counterparts. 171 candidate counterparts are detected only in the i' -band. These sources are good qLMXB and CV candidates as they are X-ray bright and likely located in the Bulge.

Cone search capability for table J/MNRAS/458/4530/table1 (List of the pointing centre and the seeing towards each field in the r'-band)

Cone search capability for table J/MNRAS/458/4530/mercat1 (merged catalogues with rgiHalpha data (among 3,144,075 stars))

Cone search capability for table J/MNRAS/458/4530/mercat2 (merged catalogues with riHalpha data (among 38,387,310 stars))

Cone search capability for table J/MNRAS/458/4530/conserv (Most likely optical counterparts of the most conservative determined from the likelihood ratio method (table 7 of the paper))

Cone search capability for table J/MNRAS/458/4530/nohalpha (Most likely optical counterparts determined with only r' and i' detections from the likelihood ratio method (table 7 of the paper))

Cone search capability for table J/MNRAS/458/4530/onlyi (Most likely optical counterparts determined with only i' detections from the likelihood ratio method (table 7 of the paper))