A seal for a piezoactuator in a fuel injector as simply, reliably and, in respect of the useful life of the piezoactuator, as favorably as possible has a support element (28), positioned on terminal posts (20) projecting in an axial direction (A) out of the piezoactuator (12) and pressed in an axial direction toward a top arrangement (14, 18) of the piezoactuator (20). An external sealing ring (36) is clamped along a circumferential region (14) of the top arrangement between the support element (28) and the top arrangement. Internal sealing rings (38) each enclose one of the terminal posts (20) and are each clamped between a face of the support element (28) facing radially inward and a circumferential face of the terminal post (20).