Data is a plural of datum, which is originally a Latin noun meaning “something given.”
Today, data is used in English both as a plural noun meaning “facts or pieces of information” ( These data are described more fully elsewhere) and as a singular mass noun meaning “information”: Not much data is available on flood control in Brazil.
It is almost always treated as a plural in scientific and academic writing. In other types of writing it is either singular or plural. The singular datum meaning “a piece of information” is now rare in all types of writing. In surveying and civil engineering, where datum has specialised senses, the plural form is datums.
Ripcurlgirl is correct. This is one of those oddities that in common usage is almost always used as "the data is" when referring to a collective body of information. I.e., in English, we rarely speak of a data bit or a piece of data (singular). It is nearly always used as a mass noun. The problem then is the translation back to French, which uses it in plural form. So the question is, can we remember to use "les données sont" in French?