What is the name of Noah’s grandfather in the Book of Genesis?

Methuselah is Noah’s grandfather in the Book of Genesis.

Genesis 5 gives the genealogy from Adam through Seth’s line. Methuselah is the son of Enoch and the father of Lamech; Lamech is identified as Noah’s father in Genesis 5:28–29. Noah is therefore Methuselah’s grandson. The genealogy places Methuselah among the antediluvian patriarchs, the figures described as living before the Flood.

Methuselah is especially famous for the age attributed to him: Genesis 5:27 says he lived 969 years, the longest lifespan recorded in the Bible. Lamech is often mistaken for Noah’s grandfather because he is Noah’s father, while Enoch is Noah’s great-grandfather. These closely connected names make the family relationship a useful distinction when reading the genealogy.