The Government has advised people who are not vaccinated to avoid high-risk activities, including international travel.
Thousands of holidaymakers will pass through Irish airports on Monday as travel restrictions in and out of the country are lifted.
From Monday, it is possible to travel to Ireland from countries within the EU, Iceland, Lichtenstein, Norway and Switzerland with no requirement to quarantine if the traveller has valid proof of being fully vaccinated, having recovered from Covid-19 or have had a negative PCR test in the last 72 hours.
Travellers coming from other countries, including Great Britain, will not have to quarantine if they have valid proof that they are fully vaccinated or recovered from Covid-19.
Those who travel on the basis of a negative PCR test will have to self-quarantine but this can be ended if they receive a second negative PCR test taken from day five.
Ireland has implemented the EU Covid Certificate, allowing people who are fully vaccinated to travel freely.
The certificate has been in place in other EU countries since July 1.
The lifting of restrictions on travel will see thousands of people going on holidays while others will travel back to Ireland to visit family and friends.
How many Covid certs have been sent to Irish people?
More than 1.1 million Covid certificates have been emailed to people in Ireland and in excess of 600,000 have been posted.
DAA (Dublin Airport Authority) chief executive Dalton Philips said: "Today is a hugely exciting and much-anticipated day as Ireland fully reopens for international travel.
"Our operational readiness team, encompassing every department across both airports, has been planning extensively for this day so that all our customers have as safe and as pleasant an experience when travelling through our airports.
"The global pandemic has taken an enormous toll and people are looking forward to reconnecting with family and friends overseas who they haven't seen for almost a year and a half.
"We have been waiting patiently for international travel to resume and it is wonderful to see customers coming through the doors of our terminals again for leisure and business travel.
"There is a great buzz and air of excited anticipation at our airports.
"We have missed our passengers, our airlines have missed them and our business partners have missed them."
What impact has Covid had on travel and tourism?
Covid-19 has had a crippling effect on every aspect of the travel and tourism sector.
"Dublin and Cork Airports have experienced a loss of over 43 million passengers in the past 16 months," Mr Philips added.
"We are working tirelessly to restore the vital connectivity that Ireland has lost during that time."
Aer Lingus chief operations officer Peter O'Neill said they are "delighted" to welcome back customers.
On Monday, the airline will operate 66 flights compared to 346 on the same date in 2019.
Mr O'Neill said: "Some customers coming to the airport today - or in the coming weeks - may be nervous, unsure or simply unfamiliar with flying. We understand that.
"Our people are trained to ensure that our customers have a safe and comfortable journey.
"We are delighted to once again be able to do what we do best for more customers - deliver safe international travel.
"Thanks to the air filtration systems on board all of our aircraft, and how air flow is managed on-board, it has been proven that the only other indoor environment with comparable air-quality is an operating theatre."
Passengers are being advised to arrive at the airport at least two hours for European flights, and three hours for US travel.
It comes as nearly 80% of the adult population have received a first dose of Covid-19 vaccine.
How do you know when you are fully vaccinated?
Chief Medical Officer Dr Tony Holohan explained when people are fully vaccinated.
He said: "If you received Pfizer, you have to wait a week after your second dose, which is five weeks after the first dose.
"If Moderna is your vaccine, you have to wait for two weeks after your second dose, which is six weeks after your first dose.
"If AstraZeneca is your vaccine, you have to wait two weeks after your second dose, and if Janssen is your vaccine, it's a single dose and you have to wait two weeks after that dose.
"Once you've gotten to that point, the benefits of the vaccination then are available to you.
"That means that people who want to meet up indoors with other vaccinated people, we no longer have a limit on the number of people who can that."
