New CSO figures show 227,000 people arrived in Ireland from abroad in July, up from 57,000 in June.
Passengers arriving from Britain accounted for 97,000, while 23,000 came from Spain and 13,000 from France.
There were also 8,000 arrivals from the US, one of the world's biggest Covid-19 hotspots.
The figures show 275,000 people left the country in July, with Britain, Spain and Poland being the most popular destinations.
Compared to July 2019 figures, there has been a 89.8 per cent drop in the number of passengers arriving into Ireland during the month, while there was a 87.4 per cent decrease in the number of people departing from Ireland.
Of the 227,300 persons arriving to Ireland in July 2020, 188,100 (82.7 per cent) arrived by air and 39,200 (17.3 per cent) arrived by sea. Of the 275,400 persons departing Ireland, 239,000 (86.8 per cent) departed by air and 36,400 (13.2 per cent) departed by sea.
The CSO also released data on domestic travel, showing that the use of public transport decreased following updated public health guidance.
Following the announcement of further Government restrictions on August 18th, the number of bus and rail journeys taken during the week commencing August 16th was 58.4 per cent lower than the week commencing March 1st.
Rail use was the most severely hit, with a decrease in use of 97.2 per cent for the week starting April 5th compared to the first week of March.
Also, information from the Road Safety Authority says 84 road fatalities occurred in the first seven months of 2020, compare to 78 for the same period last year.
