Marine salvage is the process of recovering a ship and its cargo after a shipwreck or other maritime casualty. Salvage may encompass towing, re-floating a vessel, or effecting repairs to a ship. Protecting the coastal environment from spillage of oil or other contaminants is also a high priority. Before the invention of radio, salvage services would be given to a stricken vessel by any ship that happened to be passing by. Most salvage is carried out by specialist salvage firms with dedicated crew and equipment. The legal significance of salvage is that a successful salvor is entitled to a reward, which is a proportion of the total value of the ship and its cargo. The amount of the award is determined subsequently at a "hearing on the merits" by a maritime court in accordance with Articles 13 and 14 of the International Salvage Convention of 1989. The common law concept of salvage was established by the English Admiralty Court, and is defined as "a voluntary successful service provided in order to save maritime property in danger at sea, entitling the salvor to a reward"; and this definition has been further refined by the 1989 Convention.

Originally, a "successful" salvage was one where at least some of the ship or cargo was saved, otherwise the principle of "No Cure, No Pay" meant that the salvor would get nothing. In the 1970s, a number of marine casualties of single-skin-hull tankers led to serious oil spills. Such casualties were unattractive to salvors, so the Lloyd's Open Form (LOF) made provision that a salvor who acts to try to prevent environmental damage will be paid, even if unsuccessful. This Lloyd's initiative proved so advantageous that it was incorporated into the 1989 Convention.

All vessels have an international duty to give reasonable assistance to other ships in distress in order to save life, but there is no obligation to try to salve the vessel. Any offer of salvage assistance may be refused; but if it is accepted a contract automatically arises to give the successful salvor the right to a reward under the 1989 Convention. Typically, the ship and the salvor will sign up to an LOF agreement so that the terms of salvage are clear. Since 2000, it has become standard to append a SCOPIC ("Special Compensation – P&I Clubs") clause to the LOF, so as to circumvent the limitations of the "Special Compensation" provisions of the 1989 Convention (pursuant to the case of The Nagasaki Spirit).