The Secretary-General of the European Commission is the senior civil servant of the European Commission. The Secretary-General, who is responsible to the President of the European Commission, is in charge of the various Directorates-General, headed by Directors-General.
His/her personal staff form the Secretariat-General of the European Commission.
List of Secretaries-General of the European Commission
References
Secretary-General of the European Commission Wikipedia(Text) CC BY-SA