A custodian bank, or simply custodian/depository, is the institution responsible for physically or electronically safeguarding the financial assets (shares, bonds, etc.) held by customers and dealing with all events related to that possession.

The shares acquired through direct trading on the stock exchange are held in custody by the financial institution that carried out the transaction. If the shares were acquired as a result of the purchase of old telephone lines and have never been traded, the custodian of the shares is Banco do Brasil.