Santomense originated on the island of São Tomé (Gulf of Guinea) at the beginning of the 16th century out of the contact between Portuguese and West African languages, especially from Nigeria and Angola. Contrarily to what has been claimed until now, I believe that Santomense is a tonal language with two tones, H and L, whereby some low tones might be better defined as neutral. In Santomense, tone is used for lexical distinctions, but also for grammatical purposes, especially for the distinction between nouns and verbs. As all of the known substrate languages of Santomense are tonal, there is no doubt that the origin of the tonal system of Santomense lies in the substrate languages. However, more research is needed in order to find out how Santomense’s tonal system functions and how this system is related to the system of one or more of its substrate languages.