With Felipe by her side, Letizia gave birth to Sofia at 4:50 p.m. through a Cesarean section. The baby weighed 7.3 pounds.
Both mother and child were doing fine, said a visibly moved and happy Felipe later that day at a news conference attended by the team of doctors who assisted the birth the Ruber International Clinic in northern Madrid.
The new princess, named after her grandmother, Spain's Queen Sofia, becomes third in line to the throne after her father, Crown Prince Felipe, and sister Leonor, born in at the same hospital in October 2005.
A former TV anchorwoman, Letizia became Spain's crown princess in May 2004 when she married Felipe in a glamorous royal wedding ceremony in Madrid.
Letizia was seen entering Ruber Internacional by a group of journalists and photographers who had been camped outside the hospital for days.