He was a Hebrew patriarch and the grandfather of Noah. Not much is known about him, other than his extraordinary lifespan. According to the Book of Genesis (5:27), Methuselah lived 969 years. If true, this would make Methuselah the longest-lived human by over 840 years.
Methuselah died in the year of the Great Flood. Some interpret this as God waiting for Methuselah to die before causing the Great Flood.
Methuselah came from a line of long-lived individuals. His father Enoch was 65 years old when Methuselah was born. Enoch then lived another 300 years and had other sons and daughters after Methuselah. Altogether Enoch lived 365 years. When Methuselah was 187 years old, he had a son named Lamech. After having Lamech, Methuselah lived another 782 years and had other sons and daughters. Methuselah's great-great-great-great-grandfather was Seth whose parents were Adam and Eve. Lamech (Methuselah's son) is the father of Noah.

