The baby was found alone and abandoned at about 15:30 local time on Friday on Steelstown Road.
Police said the child was tended to at the scene by their officers and medical staff. She was taken to Tallaght Hospital.
Her condition is described as stable.
Police said they were concerned for the welfare of the child's mother and were appealing for her to seek immediate medical treatment and contact them.

In less than 24 hours, the country's chosen to leave the European Union, abandoning an institution, a concept that's been part of the fabric our institutions since the 1970s.
As a result, the prime minister has left his job. Some Labour MP s are trying to unseat their leader. And Scotland faces another referendum on the other union.
Tonight it's not clear who'll be running the country in three months time. It's not certain if the leader of the opposition will stay in post beyond the weekend.
But remember, this was not an overwhelming surge to one side. Decisive yes, but a move in the margins.
Yet in a referendum - a binary vote - that produces a result that could change everything for generations.
It is not so much that politics has been turned upside down - but the conventional rules, the expectations - have been scrapped by one decision.
The prime minister's judgement, his mistaken analysis of how to win the public over, cost his job.
And almost the entire establishment's appeal to the electorate was rejected. One member of the cabinet pointed to the problem: "they don't believe us".
Right now, it is not at all inevitable that's a problem the current generation of politicians will ever be able to fix.

The pair have signed two-year deals with Carlton Fairweather's WSL 1 side.
Staniforth, 23, made her Lady Black Cats debut aged 16 and helped the club to the FA Womens' Premier League North title and 2009 Womens' FA Cup final.
Canada international Sjoman, 28, has played in America, Germany and England prior to her last move to Glasgow.
"They are two players with fantastic experience at the very top level of the game and will bring so much to our squad in terms of competition and quality," Fairweather told the club website.
A newborn baby girl has been found close to business premises in Rathcoole, County Dublin.
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Tourists and members of the public drifted to Westminster's College Green - to witness this day, and also, perhaps, just to make sense of what's going on.
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Sunderland Ladies have re-signed midfielder Lucy Staniforth from Liverpool and added defender Kylla Sjoman from Scottish side Celtic.