The 'March For Our Lives' protest was organised by survivors of the Florida school shooting
Rallies are due to take place in Cork, Dublin and Belfast this afternoon in solidarity with a major gun control protest in the US.
Over 800 protests are taking place across the US calling for stricter gun control laws.
Meanwhile solidarity protests are being held in 27 countries around the world.
The 'March For Our Lives' (MFOL) protest was organised by survivors of the Valentine's Day shooting at Marjory Stoneman Douglas High School in Parkland, Florida.
17 people were killed when a former student opened fire at Stoneman Douglas High School in Parkland, just north of Miami.
In the weeks since the attack, the MFOL movement has gained a number of celebrity supporters, raised money and even persuaded various businesses to cut ties to the National Rifle Association (NRA).
The biggest gathering is due to take place in Washington DC later today.
In a statement, rally organisers Democrats Abroad Ireland said the Irish demonstrations aim to global support for gun control movement in the wake of the Florida attack.
It said it hoped to, “show the US government that the world is watching; to fight for our right to safety in the US; and to hold lawmakers accountable and demonstrate that the majority of [US] voters want gun reform now.”
The Washington demonstration will get underway at 4pm (Irish time) this afternoon, with 500,000 people are expected to march.
People in other time zones have already been showing their support.
Around 100 people held a rally in Sydney, Australia this morning to show their support for the US teenagers.
Protester Jennifer Smith said she had been inspired by the young people who had stepped forward to say "enough is enough".
She added: "Sadly, they're doing the jobs that adults have not been able to do, and I think this is really going to be the turning point where people stand up, they listen and it's going to change a lot of things."
Marches also took place at a number of cities in New Zealand, organised by university students.
Other marches are due to take place in Asia, Africa, South America and Europe.
The Dublin rally gets underway at 3pm outside the Us Embassy in Ballsbridge.