The invention relates to a single-piece fan blisk (14) for a turbojet, this blisk (14) comprising a hub (16) with a general shape of revolution about a rotation axis (AX) and comprising an external peripheral face (18) of revolution extending radially towards the rotation axis at an upstream face (19) and a downstream face both of which are in the form of rings. This hub (16) supports radially oriented blades (17) at its external peripheral face (18), each comprising a base through which it is connected to this external peripheral face (18), each blade (17) having a leading edge (22) and a trailing edge (23) that are radially oriented. The spacing between the upstream face (19) and the downstream face of the hub (16) along the rotation axis (AX) is less than the distance separating the leading edge (22) from the trailing edge (23) of each blade.