The discovery, which was made outside the vicarage of St Peter’s Church in Hough Lane, Bramley, was reported to West Yorkshire Police at 9.18am today.
The baby boy was then rushed to Leeds General Infirmary in an ambulance but was pronounced dead a short time later.
West Yorkshire Police said it was “extremely concerned” for the welfare of the baby’s mother, as they urged anyone with any information to contact them as soon as possible.
A spokesman for the force said: “At 9.18am today, police received a report of a newborn baby having been found outside the vicarage of St Peter’s Church, in Hough Lane, Bramley.
“The male child was taken to Leeds General Infirmary by ambulance but was pronounced dead a short time later.
“Enquiries are ongoing to identify the child and his mother and officers are keen to hear from anyone with any information that could assist the investigation.
“Officers are extremely concerned for the mother’s welfare and the fact that she may need urgent medical attention given the potential circumstances surrounding the baby’s birth.
“Anyone with information or who may have seen anyone in the vicinity of the vicarage overnight is asked to contact police via 101 quoting log number 354 of November 23.”