Judaism has different names given to God, which are considered sacred: יהוה (YHWH), אֲדֹנָי (Adonai transl. my Lord[s]), אֵל (El transl. God), אֱלֹהִים (Elohim transl. Gods/Godhead), שַׁדַּי (Shaddai transl. Almighty), and צְבָאוֹת (Tzevaoth transl. [Lord of] Hosts); some also include I Am that I Am. Early authorities considered other Hebrew names mere epithets or descriptions of God, and wrote that they and names in other languages may be written and erased freely. Some moderns advise special care even in these cases, and many Orthodox Jews have adopted the chumras of writing "G-d" instead of "God" in English or saying Ṭēt-Vav (טו, lit. '9-6') instead of Yōd-Hē (יה, '10-5', but also 'Jah') for the number fifteen or Ṭēt-Zayin (טז, '9-7') instead of Yōd-Vav (יו, '10-6') for the Hebrew number sixteen.

The names of God that, once written, cannot be erased because of their holiness are the Tetragrammaton (YHWH), Adonai, El, Elohim, Shaddai, Tzevaot; some also include I Am that I Am, from which "YHWH" is believed to be derived. In addition, the name Jah—because it forms part of the Tetragrammaton—is similarly protected. The tanna Jose ben Halafta considered "Tzevaot" a common name in the second century and Rabbi Ishmael considered "Elohim" to be one. All other names, such as "Merciful", "Gracious" and "Faithful", merely represent attributes that are also common to human beings.

Also abbreviated Jah, the most common name of God in the Hebrew Bible is the Tetragrammaton, יהוה. The Hebrew script is an abjad, and thus vowels are often omitted in writing. The Tetragrammaton is sometimes rendered with vowels, though it is not known which vowels were used originally. Direct transliteration is avoided in Jewish custom.

Modern Rabbinical Jewish culture forbids pronunciation of this name. In prayers it is replaced by saying the word אֲדֹנָי (Adonai, Hebrew pronunciation: [adoˈnaj] 'My Lords', Pluralis majestatis taken as singular), and in discussion by HaShem 'The Name'. Nothing in the Torah explicitly prohibits speaking the name and the Book of Ruth shows that it continued to be pronounced as late as the 5th century BCE. Mark Sameth argues that only a pseudo name was pronounced, the four letters יהוה (YHVH, YHWH) being a cryptogram which the priests of ancient Israel read in reverse as huhi, 'he–she', signifying a dual-gendered deity, as earlier theorized by Guillaume Postel (16th century) and Michelangelo Lanci ^[it] (19th century). It had ceased to be spoken aloud by at least the 3rd century BCE, during Second Temple Judaism. The Talmud relates, perhaps anecdotally, that this began with the death of Simeon the Just. Vowel points began to be added to the Hebrew text only in the early medieval period. The Masoretic Text adds to the Tetragrammaton the vowel points of Adonai or Elohim (depending on the context), indicating that these are the words to be pronounced in place of the Tetragrammaton (see Qere and Ketiv), as shown also by the pronunciation changes when combined with a preposition or a conjunction. This is in contrast to Karaite Jews, who traditionally viewed pronouncing the Tetragrammaton as a mitzvah because the name appears some 6800 times throughout the Tanakh; however, most modern Karaites, under pressure and seeking acceptance from mainstream Rabbinical Jews, now also use the term Adonai instead. The Beta Israel pronounce the Tetragrammaton as Yahu, but also use the Geʽez term Igziabeher.

The Tetragrammaton appears in Genesis and occurs 6,828 times in total in the Biblia Hebraica Stuttgartensia edition of the Masoretic Text. It is thought to be an archaic third-person singular of the imperfective aspect of the verb "to be" (i.e., "[He] is/was/will be"). This agrees with the passage in Exodus where God names himself as "I Will Be What I Will Be" using the first-person singular imperfective aspect, open to interpretation as present tense ("I am what I am"), future ("I shall be what I shall be"), or imperfect ("I used to be what I used to be").

Rabbinic Judaism teaches that the name is forbidden to all except the High Priest of Israel, who should only speak it in the Holy of Holies of the Temple in Jerusalem on Yom Kippur. He then pronounces the name "just as it is written." As each blessing was made, the people in the courtyard were to prostrate themselves completely as they heard it spoken aloud. As the Temple has not been rebuilt since its destruction in 70 CE, most modern Jews never pronounce YHWH but instead read אֲדֹנָי (Adonai, Hebrew pronunciation: [adoˈnaj], 'My Lords', Pluralis majestatis taken as singular) during prayer and while reading the Torah and as HaShem 'The Name' at other times. Most English translations of the Bible write "the LORD" for YHWH, and "the LORD God" or "the Lord GOD" for Adonai YHWH instead of transcribing the name. The Septuagint may have originally used the Hebrew letters themselves amid its Greek text, but there is no scholarly consensus on this point.

אֲדֹנָי (ăḏonāy, Biblical Hebrew pronunciation: [aðoˈnɔːj], lit. transl. My Lords, pluralis majestatis taken as singular) is the possessive form of adon ('Lord'), along with the first-person singular pronoun enclitic. As with Elohim, Adonai's grammatical form is usually explained as a form akin to the "royal we". In the Hebrew Bible, the word is nearly always used to refer to God (approximately 450 occurrences). As the pronunciation of the Tetragrammaton came to be avoided in the Hellenistic period, Jews may have begun to drop the Tetragrammaton when presented alongside Adonai and subsequently to expand it to cover for the Tetragrammaton in the forms of spoken prayer and written scripture. Owing to the expansion of chumra, the idea of 'building a fence around the Torah', the word Adonai itself has come to be too holy to say for Orthodox Jews outside of prayer, leading to its replacement by HaShem ('The Name').

The singular forms adon and adoni ('my lord') are used in the Hebrew Bible as royal titles, as in the First Book of Samuel, and for distinguished persons. The Phoenicians used it as a title of Tammuz (the origin of the Greek god's name Adonis). It is also used very occasionally in Hebrew texts to refer to God (e.g. Psalm 136:3). Deuteronomy 10:17 has the Tetragrammaton alongside the superlative constructions "God of gods" (elōhê ha-elōhîm, literally, "the gods of gods") and "Lord of lords" (adōnê ha-adōnîm, "the lords of lords": כִּי יְהוָה אֱלֹהֵיכֶם הוּא אֱלֹהֵי הָאֱלֹהִים וַאֲדֹנֵי הָאֲדֹנִים; JPS 2006: "For your God יהוה is God supreme and Lord supreme").