From today, employees can return to work if they have low levels of interaction with their colleagues.
Some pubs can reopen while barbers and hairdressers are welcoming back customers.
Small social gatherings, up to 50 people, can be held indoors while outdoor gatherings up to 200 people are allowed.
Creches and pre-schools for children of essential workers can now reopen in a "phased manner" while childminders who look after them can work again.
Non-essential retail outlets, with street level entrances and exits, and playgrounds can also reopen.
The move is part of the progression from phase two to phase three of its five step system to lift the coronavirus lockdown restrictions.
Phase one, on 18 May, saw people allowed to meet from different households outside and childcare to take place for just healthcare workers.
Phase two, on 8 June, allowed people from different homes to meet inside and libraries to reopen.
The next stage, phase four, will take place on 20 July, and phase 5 on 10 August.
Ceira Lambert, the owner of Ceira Lambert Hair Consultancy in Shankhill, County Dublin, told Sky News she was "nervous and excited" about reopening her shop for the first time in three months.
Speaking about how the COVID-19 lockdown has affected her business, she said: "It's been stressful, really stressful. But we just can't wait to get back at it.
"Every client has to wear a mask, everyone has to sanitise as they arrive, everyone is then shown to a chair.
"We 're going to keep the top two stations free. We will only be able to use every second chair now to keep the distance
"We have disposable gowns and full PPE."
There are around 25,400 cases of COVID-19 in Ireland while 1,735 people have died after contracting the virus.
Sky's Ireland correspondent, Stephen Murphy, was at Ceira Lambert Hair Consultancy for the reopening on Monday morning.
The phones haven't stopped ringing at the Ceira Lambert Hair Consultancy in Shankill, which finally reopened its doors today after 15 weeks.
Owner Ceira Lambert and her 12 staff have been receiving the Irish government's COVID-19 payment since shutting their doors in March, and the business has lost "thousands of euro".
"We just need to get back, get business back, get our clients in and hope that in six months' time everything will be ok. But I'm so relieved to be open again today, it's great."
Perspex screens, electronic thermometers and lots of PPE will confront customers returning to salons.
Stylist Paul Scott is wearing a plastic gown, facemask and full face visor as he works on a customer. "Oh God, it's been a long four months," he tells us. "It's been a long time coming, and just a real relief to get back to work."
For customers like Fiona O'Neill, wrapped in a disposable plastic gown and wearing a face covering, it's been a long wait.
"It's great to get back to the hairdresser", she says.
"It's been four months and I'm getting a cut and colour today, it's badly needed.
"I feel safe here, the PPE that everyone's wearing, and having your temperature checked means I'm comfortable enough, I think precautions are being taken."
It's not just the women of Ireland scrambling for a hair cut.
Several Dublin barbershops opened up at the stroke of midnight, including the Grafton Barber, which reported brisk trade, and busy queues outside in the wet Dublin night.