In this thesis, the European Investment Bank (EIB) is subject to law-historical analysis. To this end, its historical development, starting from the first legal foundation, its former function as well as its radius of action for the Foundation of the EEC Treaty in 1957 and its further development to its current status, is examined. Up to now, new shareholders, new legal bases, other objects and a revised range have been introduced. The original goal of the EIB has not changed, however, over the years, it has been supplemented by other objects. In the beginning, only financing operations within the Member States were realized. From 1962 onwards, it grants loans to third countries for selected projects. Since 1993, it assigns loans to the third countries themselves. Initially, the EIB had six shareholders. Since the establishment of the European Union (EU) in 1993, the EIB is its means and represents its interests. Today, all 28 Member States of the EU are the shareholders of EIB. Originally, it was promoting regional balance between the Member States by granting loans. Today, the EIB operates worldwide, still provides loans as well as guarantees and micro lending, allows capital investments and procures technical advice. The EIB is still not a bank in a classical meaning; it is no body in itself. Nevertheless, it has been a legal entity since its foundation.The EIB generates its financial resources on the international capital markets by issuing bonds. By doing so, the EIB has grown to the largest multilateral borrower and lender worldwide.