Dangerous goods are substances that are a risk to health, safety, property or the environment during transport. Certain dangerous goods that pose risks even when not being transported are known as hazardous materials (syllabically abbreviated as HAZMAT or hazmat). An example of dangerous goods is hazardous waste which is waste that threatens public health or the environment.

Hazardous materials are often subject to chemical regulations. Hazmat teams are personnel specially trained to handle dangerous goods, which include materials that are radioactive, flammable, explosive, corrosive, oxidizing, asphyxiating, biohazardous, toxic, poisonous, pathogenic, or allergenic. Also included are physical conditions such as compressed gases and liquids or hot materials, including all goods containing such materials or chemicals, or may have other characteristics that render them hazardous in specific circumstances.

Dangerous goods are often indicated by diamond-shaped signage on the item (see NFPA 704), its container, or the building where it is stored. The color of each diamond indicates its hazard, e.g., flammable is indicated with red, because fire and heat are generally of red color, and explosive is indicated with orange, because mixing red (flammable) with yellow (oxidizing agent) creates orange. A nonflammable and nontoxic gas is indicated with green, because all compressed air vessels were this color in France after World War II, and France was where the diamond system of hazmat identification originated.

The most widely applied regulatory scheme is that for the transportation of dangerous goods. The United Nations Economic and Social Council issues the UN Recommendations on the Transport of Dangerous Goods, which form the basis for most regional, national, and international regulatory schemes. For instance, the International Civil Aviation Organization has developed dangerous goods regulations for air transport of hazardous materials that are based upon the UN model but modified to accommodate unique aspects of air transport. Individual airline and governmental requirements are incorporated with this by the International Air Transport Association to produce the widely used IATA Dangerous Goods Regulations (DGR). Similarly, the International Maritime Organization (IMO) has developed the International Maritime Dangerous Goods Code ("IMDG Code", part of the International Convention for the Safety of Life at Sea) for transportation of dangerous goods by sea. IMO member countries have also developed the HNS Convention to provide compensation in case of dangerous goods spills in the sea.

The Intergovernmental Organisation for International Carriage by Rail has developed the regulations concerning the International Carriage of Dangerous Goods by Rail ("RID", part of the Convention concerning International Carriage by Rail). Many individual nations have also structured their dangerous goods transportation regulations to harmonize with the UN model in organization as well as in specific requirements.

The Globally Harmonized System of Classification and Labelling of Chemicals (GHS) is an internationally agreed upon system set to replace the various classification and labeling standards used in different countries. The GHS uses consistent criteria for classification and labeling on a global level.

Dangerous goods are assigned to UN numbers and proper shipping names according to their hazard classification and their composition. Dangerous goods commonly carried are listed in the Dangerous Goods list.

Examples for UN numbers and proper shipping names are: