Plans for a telecommunications mast at Cappagh Road have been refused by An Bord Pleanala.
The new mast would replace an existing pole that must be removed because it conflicts with the planned city bypass.
The site is located to the north of the roundabout that serves Cappagh Road and the Western Distributor Road.
The new telecommunications pole would replace an existing monopole around 100m to the south-east, which has to be removed due to the planned Galway City Ring Road.
It serves the Vodafone, Eir and Three networks - all three of which have written in support of the plans, which they argue is vital to maintain 4G and 5G signal quality.
But city planners rejected the plans in June, largely because a temporary access road would still lie within the bypass route corridor.
In making an appeal, Vantage Towers Ltd offered an alternative long-term track and entrance.
But An Bord Pleanala has rejected the plans, finding that the material change was not part of the original application and public notice.
