Danica May Camacho was born just before midnight Sunday in Manila.
Her parents were met by top U.N. officials who gave them a small cake. They were also given a scholarship grant for the child's schooling.
The observation is symbolic because it's impossible to pinpoint the arrival of the seven billionth birth.
Many experts say it's not necessarily something to celebrate.
"The big problem is that in the poorest countries, families are still having six, seven or eight children. That's what's putting this tremendous growth of population continuing. In the high income countries, fertility rates have come down to two children on average or even less," said Jeffrey Sachs, director of the Earth Institute.
Demographers say it took until 1804 for the world to reach its first billion people, and a century more until it hit 2 billion in 1927. The twentieth century, though, saw things begin to cascade: 3 billion in 1959; 4 billion in 1974; 5 billion in 1987; 6 billion in 1998.
The U.N. estimates the world's population will reach 8 billion by 2025 and 10 billion by 2083. But the numbers could vary widely, depending on everything from life expectancy to access to birth control to infant mortality rates.
The Associated Press contributed to this report.