The present disclosure relates to a mobile crane that comprises an undercarriage having a chassis and comprises a superstructure that is rotatable about a vertical axis relative to the undercarriage and has a telescopic boom at whose tip a boom head is arranged. The boom has holding means at one side for the support of a folding boom that can be releasably installed at the boom head. The boom laterally has a console and a holding element arranged between the console and the boom head. The folding boom is pivotable about a vertical axis of the holding element for the installation at the boom head, while it is supported on the console. In accordance with the present disclosure, a first securing device is arranged in the region of the console by means of which a movement of the folding boom deviating from a pivot movement about a vertical axis can be limited. The present disclosure furthermore relates to a folding boom for a crane.