International Convention on Safety of Life at Sea adopted in 1974 by IMO. The 1974 Convention has been modified on a number of occasions: changes were introduced, amendments were adopted and new chapters were added. The Convention applies only to ships engaged on international voyages, it does not apply to ships of war and troopships, cargo ships of less than 500 gross tonnage, ships not propelled by mechanical means, wooden ships of primitive build, pleasure yatchts not engaged in trade and fishing vessels.
Further reading: SOLAS Consolidated Edition 2004.