Galicia is a region located in the north-west of the Iberian Peninsula, where, historically, illegitimacy was often high compared with levels elsewhere in Europe. At the same time, Galicia's coastal and inland areas have always differed greatly in terms of farming structure, population growth, migration patterns, family types and inheritance systems. The aim of this article is to establish to what extent the trends in and levels of illegitimacy between 1570 and 1899 were influenced by these different historical contexts. It also offers an in-depth examination of unmarried mothers, showing that the trend towards bearing more than one illegitimate child rose over time. Ultimately, the article argues that illegitimacy is best studied at a local or regional level, rather than at the macro level that historians have often employed elsewhere in Europe.