A neonatal intensive care unit (NICU), also known as an intensive care nursery (ICN), is an intensive care unit (ICU) specializing in the care of ill or premature newborn infants. The NICU is divided into several areas, including a critical care area for babies who require close monitoring and intervention, an intermediate care area for infants who are stable but still require specialized care, and a step down unit where babies who are ready to leave the hospital can receive additional care before being discharged.

Neonatal refers to the first 28 days of life. Neonatal care, as known as specialized nurseries or intensive care, has been around since the 1960s.

The first American newborn intensive care unit, designed by Louis Gluck, was opened in October 1960 at Yale New Haven Hospital.

NICU is typically directed by one or more neonatologists and staffed by resident physicians, nurses, nurse practitioners, pharmacists, physician assistants, respiratory therapists, and dietitians. Many other ancillary disciplines and specialists are available at larger units.

The term neonatal comes from neo, "new", and natal, "pertaining to birth or origin".