A Long Island couple’s safe deposit box is so secure, even they can’t get into it, they say in a lawsuit.

Brenda and Robert Fox have kept $48,000 in jewel­ry in a box at a Chase Bank in Huntington since 2009.

The Foxes had no trouble with the setup until last year, when Brenda was told there was no record of her owning the box.

Even after a supervisor opened it with Brenda’s key, managers declined to let her have the belongings inside because recently computerized records listed a different owner, the Foxes say in Brooklyn federal court.

The Foxes want the bank to return their possessions, let them have the safe deposit box or pay unspecified damages.