A State Emergency Service (SES) is an Australian volunteer organisation that provides emergency help during and after declared (natural or otherwise) disasters. The SES is also the primary or secondary agency for emergencies, such as storm damage,flood damage, building damage, traffic hazards and road crash rescue. In other scenarios the SES may provide a support role to other agencies, particularly police and fire. The SES is operational 24 hours a day 7 days a week.

The Civil Defence Service began in Australia in 1955. It was formed as a precaution to any potential attacks on Australian soil. The name was changed to the "State Emergency Service" (abbreviated to "SES") during the 1970s, to reflect a change of emphasis into providing emergency help related to floods, storms and other natural emergencies. Every state and territory in Australia has its own State (or Territory) Emergency Service, and there are 43,000 volunteers spread across the country. Each state or territory is broken into regions, then units, and finally groups or teams.

Emergency services are organizations which ensure public safety and health by addressing different emergencies. Some agencies exist solely for addressing certain types of emergencies whilst others deal with ad hoc emergencies as part of their normal responsibilities. Many agencies will engage in community awareness and prevention programs to help the public avoid, detect, and report emergencies effectively.

The availability of emergency services depends very heavily on location, and may in some cases also rely on the recipient giving payment or holding suitable insurance or other surety for receiving the service.

There are three main emergency service functions:

In some countries (e.g. the UK) these three functions are performed by three separate organisations in a given area. However there are also many countries where fire, rescue and ambulance functions are all performed by a single organisation.

Emergency services have one or more dedicated emergency telephone numbers reserved for critical emergency calls. In some countries, one number is used for all the emergency services (e.g. 911 in the US, 999 in the UK). In some countries, each emergency service has its own emergency number.

A state of emergency is a governmental declaration that may suspend some normal functions of the executive, legislative and judicial powers, alert citizens to change their normal behaviours, or order government agencies to implement emergency preparedness plans. It can also be used as a rationale for suspending rights and freedoms, even if guaranteed under the constitution. Such declarations usually come during a time of natural or man made disaster, during periods of civil unrest, or following a declaration of war or situation of international or internal armed conflict. Justitium is its equivalent in Roman law.

In some countries, the state of emergency and its effects on human rights and freedoms and governmental procedure are regulated by the constitution and/or a law that limits the powers that may be invoked. Rights and freedoms may be suspended during an emergency, for instance, freedom of movement, but not non-derogable rights. In many countries it is illegal to modify the emergency law or the constitution during the emergency.