The budget carrier will launch a twice-weekly Manchester-Santorini service, and weekly Liverpool-Kos and Teesside-Corfu flights, in July.
It also plans to boost frequencies on three existing routes.
Its Manchester-Chania service will increase to from three-times-weekly to four-times-weekly and its Stansted-Rhodes service from three-times-weekly to six-times-weekly.
These changes will come into effect in July.
Ryanair will also up its twice-weekly Manchester-Chania service to three-times-weekly in August.
Jason McGuinness, Ryanair’s director of commercial, said: "As vaccination roll-out programmes continue in the coming months, air traffic is set to soar and we are delighted to announce three new routes and extra flights connecting the UK to a host of popular Greek destinations this summer."
Greece has confirmed it will waive its quarantine rules for UK travellers who have been vaccinated against Covid-19 or can provide evidence of a recent negative test for Covid-19.
The country has said it will reopen to UK visitors as soon as international travel is permitted by the UK government, although the UK government is yet to announce details of how Greece will be categorised under a new traffic light system set to govern travel from 17 May.
