In the Book of Genesis, Shem is named first among Noah's three sons. Genesis 5:32 lists Noah as the father of Shem, Ham, and Japheth, and the same order appears in several later passages. Shem is therefore the canonical answer when the question asks which son is listed first.
The three sons are important to the narrative after the Flood. Genesis describes them leaving the Ark with Noah and their wives, and later presents them as ancestors of different peoples. The text does not necessarily establish that the listing order is a simple statement of age in every passage, which is why traditions have debated the brothers' relative ages.
Shem also has special importance in biblical genealogy: Genesis traces a line from Shem through several generations to Abram, later known as Abraham. The term “Semitic” was coined much later and is derived from Shem's name, although modern language classification is more complex than the biblical genealogy.