Bottomry, in maritime law, a contract by which the owner of a ship, or the master as his agent, hypothecates or binds the ship as security for the repayment of money advanced for the use of the ship. The name is derived from bottom, that is, keel, a figure by which the vessel itself is designated. In form it is a bond, by which, in consideration of the money lent, the borrower undertakes to repay it if the ship accomplishes its voyage, and pledges the ship for the performance of the undertaking. If the ship should be lost, the debt would be lost, that is, so far as it depends upon the bottomry bond; and in consideration of this risk, a higher rate of interest may be agreed for than is allowed in other contracts. In case of partial damage to the ship, it is usually provided that the lender shall bear his proportion of it, which will be the proportion the amount lent bears to the whole value of the vessel. The lender is not entitled to possession of the vessel, not even when the debt becomes due (unless it should be so expressly stipulated in the bond), but may enforce payment of the debt by a decree of a court of admiralty for sale of the vessel.

The master is not authorized to enter into this species of contract except in a case of necessity, usually when the vessel is in some foreign port, and he .has no other resources for obtaining the necessary supplies. It would impair the obligation of the bond if there were in fact means of getting such supplies without hypothecation of the vessel, and this was known to the lender. A bottomry bond is a pledge of the ship and freight; a respondentia bond is a pledge of the cargo; but both ship and cargo may be included in the same instrument. As respects the cargo there is not strictly a lien for the money lent, except in case of partial loss; but if the voyage is successfully performed, the obligation is merely personal, unless an express provision be inserted in the bond for a specific lien upon the goods.