We compare multi-ice core data with δ18O model output for the early last interglacial Antarctic sea-ice minimum. The spatial pattern of δ18O across Antarctica is sensitive to the spatial pattern of sea-ice retreat. Local sea ice retreat increases the proportion of winter precipitation, depleting δ18O at ice core sites. However, retreat also enriches δ18O because of the reduced source to-site distance for atmospheric vapour. The joint overall effect is for δ18O to increase as sea ice is reduced. Our data-model comparison indicates a winter sea-ice retreat of 67, 59 and 43 % relative to pre-industrial in the Atlantic, Indian and Pacific sectors of the Southern Ocean. A compilation of Southern Ocean sea-ice proxy data provides weak support for this reconstruction. However, most published marine core sites are located too far north of the 128,000 years BP sea ice edge, preventing independent corroboration for this sea ice reconstruction.