The old bridge that links the twin towns of Killaloe in Co Clare and Ballina in Co Tipperary will close permanently to vehicular traffic from Friday and operate as a pedestrian and cycle link across the River Shannon.
The announcement has been made by Clare and Tipperary county councils.
A new crossing for vehicles - the Brian Boru Bridge - opened in May.
It was built at a cost of €88 million and is the first new vehicular bridge across the River Shannon in more than three decades, forming part of the 6.2km Killaloe Bypass.
During a trial period, the historic narrow stone arch bridge remained open to traffic for two months and then closed to traffic for another two months.
The councils described the trial period as "successful" and said the old bridge will now serve as a pedestrian and cycle link across the River Shannon.
They said the decision follows a comprehensive process in which both local authorities recognised the importance of gathering "robust data and undertaking public engagement before deciding to prohibit vehicular traffic on the historic bridge".
Data collected before and during the trial period demonstrated that closing the bridge to vehicles did not result in any detrimental impact on traffic flows in either Ballina or Killaloe, the councils said.
"The trial period also highlighted the bridge's value as a safer environment for pedestrians and cyclists, and its suitability as a venue for local promotional and tourism events," a statement said.
It added that the majority of respondents from both Killaloe and Ballina expressed support for the continued closure of the bridge to vehicular traffic, particularly since the opening of the Brian Boru Bridge.
However, the councils acknowledged concerns raised regarding economic impact, as well as issues of accessibility and emergency service response times.
They said they remain committed to supporting businesses in both towns and to promoting Killaloe and Ballina as vibrant places for commerce and tourism.
Meanwhile, the emergency services confirmed they did not anticipate any significant impact on their operations because of this decision.
The Department of Transport, in correspondence with both councils also confirmed that the closures of the bridge to vehicle traffic aligns with national policies, including the National Sustainable Mobility Policy, the National Investment Framework for Transport in Ireland and the Road Safety Strategy.
