São Domingos is both a Sector and a city in the Cacheu Region of Guinea-Bissau.

The sector contains the main border checkpoint to Senegal between Jegue (on the Guinean side), Mpack on the Senegalese.

There was a Portuguese trading post at Sao Domingos (known in the local Banyum language as Buguendo) at least as early 1535, by which point it had attained a semi-unofficial status.

[1]: 145  In the late sixteenth century, however, relations between the Portuguese lançados and the native Bainuk people deteriorated.

[2] This experiment likewise failed, and the center of the lancados trade moved across the river to Cacheu.