The Mercy James Institute for Paediatric Surgery and Intensive Care located in Blantyre, Malawi's second-largest city, is the first such facility built in the country by Madonna's charity Raising Malawi.
"We will ensure that not only will it be a world-class children's hospital, but also a superior centre of learning. This is as much about healing as it is about empowerment," Madonna said at the hospital's official opening.
The singer adopted Malawian children David Banda and Mercy James in 2006 and 2009 respectively and twins Esther and Stella Mwale earlier this year. She has two other children, Lourdes and Rocco, from previous relationships.
Speaking at the event, Mercy James drew applause and ululation from the crowd after saying: "Many kids and many lives will be saved. Thank you mum, you're the bomb."
Madonna established the non-profit Raising Malawi charity in 2006 to provide health and education, particularly for girls. The charity has built 10 schools in Malawi, according to its website.
Madonna criticised Malawi's slow pace of law reform, saying it nearly prevented her from adopting Mercy James.
"It was not an easy battle," said Madonna as her voice cracked with emotion as she stood near her daughter.
"The judge refused me because I was recently divorced. We hired lawyers, went to the Supreme Court. But I never gave up, I never backed down," added the 58-year-old, who previously stirred anger among some Malawians as they felt the government allowed her to skirt laws that ban non-residents from adopting.
"I fought for Mercy and won. We fought for this hospital and won. Love conquers all."
Madonna then danced to a local song with Malawi's first lady Gertrude Mutharika.
Mutharika, who attended the hospital's launch, said "Madonna is a symbol of a motherly spirit" and that the hospital was Malawi's "national pride".
The health minister Peter Kumpalume said the hospital will help save lives of newborns in a country where infant mortality is still one of the highest in the world, but steadily declining.
"For our part, we will fully support the facility, we are bringing in doctors and drugs," Kumpalume told Reuters.
Malawi's infant mortality rate declined to 42 deaths per 1,000 live births in 2016 from 135 deaths in 1992, government data shows.
