The system enables urgent messages to be broadcast to a defined area when there is an imminent risk to life, such as wildfires or severe flooding.
It will bring the UK in line with other countries such as the US and Canada, who already have such a system in place.
A UK-wide test of the Emergency Alerts system will take place at 3pm on Sunday 23 April.
Following successful pilots in East Suffolk and Reading, the test will see people receive a message on the home screen of their mobile phone, along with a sound and vibration for up to ten seconds.
For the test, the public does not need to take any action – the sound and vibration will stop automatically after ten seconds. The alert can be swiped away or dismissed via an 'OK' button on the smartphone's home screen.
Emergency Alerts have already been used successfully in a number of other countries, including the US, Canada, the Netherlands and Japan, where it has been credited with saving lives, for example, during severe weather events.
The government has worked together with the emergency services and partners, including the Football Association and London Marathon, to make sure the national test has minimum impact on major events taking place on that day.
Chancellor of the Duchy of Lancaster, Oliver Dowden MP, said: "Put the date in your diaries – at 3pm on 23 April, we'll be testing our new national Emergency Alerts system.
"Getting this system operational with the national test means we have another tool in our toolkit to keep the public safe in life-threatening emergencies. It could be the sound that saves your life."
The National Centre for Domestic Violence (NCDV) has warned people with hidden second mobile phones to turn off the alerts to avoid revealing the location of their devices.
Sharon Bryan, head of Partnerships & Development of Domestic Abuse Services at NCDV, said: "Hidden second mobiles are an emergency lifeline for victims and survivors living under the constant threat of abuse, or worse.
"This siren test may unexpectedly reveal their presence to abusers – with disastrous consequences."
The government said it has been actively engaging with organisations working with vulnerable women and girls to ensure they are not adversely affected by the introduction of emergency alerts.
Officials have stressed that it is easy to opt out of the system if people need their phone to stay concealed, either by turning off the alerts or simply having the phone switched off during the test.
Chair of the National Fire Chiefs Council, Mark Hardingham, said: "We must use every tool at our disposal to keep people safe, and we need everyone to play their part – and the new Emergency Alerts system is one way we can do this.
"For 10 seconds, the national test may be inconvenient for some, but please forgive us for the intrusion, because the next time you hear it – your life, and the life-saving actions of our emergency services, could depend on it."
