The invention relates to an adapter (1) for a transfer device (20) for a fluid, for the connection of a container (17) containing the fluid, wherein the container (17) is closed by a pierceable closure element (18), and the adapter (1) has an attachment (4) which can be fitted sealingly, in an attachment direction, onto a container mouth closed by the closure element. A penetration element (6) is mounted on the attachment (4) in such a way that the penetration element (6) is movable, with the aid of guide means, between a rest position (R) and a withdrawal position (E), wherein the penetration element (6) has a hollow needle (9) with which the closure element (18) can be pierced in the withdrawal position (E). The adapter (1) has a connector stub (3) with a coupling for the fluid-tight connection of a further adapter (1′), and a transfer channel (10) runs from a mouth on the connector stub (3) to a mouth on the hollow needle (9), such that the mouth of the transfer channel (10) on the connector stub (3) communicates with an interior of the connected container (17) in the withdrawal position (E) of the penetration element (6). The invention is characterized in that the connector stub (3) is arranged transversely, in particular substantially perpendicularly, with respect to the attachment direction (H), preferably on the penetration element (6).
