The EU currently has 24 official languages: Bulgarian, Croatian, Czech, Danish, Dutch, English, Estonian, Finnish, French, German, Greek, Hungarian, Irish, Italian, Latvian, Lithuanian, Maltese, Polish, Portuguese, Romanian, Slovak, Slovenian, Spanish and Swedish. This is slightly less than the number of member states: 28. The reason for this is that each country can propose one of its official languages, and some countries share official languages: Belgium with France, the Netherlands and Germany; Luxembourg with France and Germany; Austria with Germany; and Cyprus with Greece.
English was not an official language of the EU when the EEC was formed in 1957. It only became an official languages of the EU after the UK (and Ireland) joined in 1973.
The other countries with English as an official language are Ireland and Malta. Each of these nominated another language as an official language of the EU: Irish and Maltese.
This brings up the question, will English be abandoned by the EU if the UK leaves the Union? It would seem quite likely, unless the EU decides to bend the rules, or Ireland or Malta decide to replace one of their languages in Brussels with English.
The French are bound to be pleased about this.