This is an introduction to a special issue on the theme ‘The Sexes and the Sciences’. Here we provide useful context for the ensuing research articles by way of discussing specific terms (‘science’ and ‘sex’), detailing relevant historiographies and presenting select, illuminating case studies. Taken as a whole, this special issue demonstrates that eighteenth‐century scientific understandings of the sexes – male and female – were diverse and debated, and that, while formal scientific institutions and publications were almost exclusively comprised of men, their gendered relationships were various, and numerous women still meaningfully contributed to science as both practitioners and patrons.