The term tetragrammaton (from Greek τετραγράμματον, meaning "[a word] having four letters") refers to the Hebrew written form of YHWH (Hebrew: יהוה‎), one of the names of the God of Israel which is used in the Hebrew Bible and elsewhere.

This written Hebrew name is generally regarded as having been pronounced as Yahweh by modern scholars, though many variant pronunciations have been proposed.

At some point a taboo on saying the name aloud developed in Judaism, and rather than pronounce the written name, other titles were substituted, including "Lord" (in Hebrew Adonai, in Greek Kyrios).

The tetragrammaton occurs 6,828 times in the Hebrew text of both the Biblia Hebraica and Biblia Hebraica Stuttgartensia. The only books it does not appear in are the Song of Songs, Ecclesiastes, and Esther. It first appears in the Hebrew text in Genesis 2:4. The letters, properly read from right to left (in Biblical Hebrew), are:

According to the Brown-Driver-Briggs Lexicon, יְהֹוָה (Qr אֲדֹנָי) occurs 6,518 times, and יֱהֹוִה (Qr אֱלֹהִים) occurs 305 times in the Masoretic Text.