In the Genesis flood narrative about Noah’s Ark, Noah was 600 years old when the flood began. Genesis 7:6 gives his age as the waters came upon the earth.
The age belongs to the biblical chronology and should not be confused with Noah’s age at his death. Genesis 9:28 says Noah lived 350 years after the flood, and Genesis 9:29 gives his total lifespan as 950 years. These figures are part of the long lifespans recorded for several early biblical patriarchs.
Noah’s sons were already adults and had wives when they entered the ark, but Genesis presents Noah’s age as the main chronological marker for the flood’s beginning. The number 600 is therefore specific to the onset of the flood, rather than to the construction of the ark or Noah’s entire life.