Jah or Yah (Hebrew: יָהּ‎, Yāh) is a short form of יהוה (YHWH), the four letters that form the tetragrammaton, the personal name of God: Yahweh, which the ancient Israelites used. The conventional Christian English pronunciation of Jah is , even though the letter J here transliterates the palatal approximant (Hebrew י Yodh). The spelling Yah is designed to make the pronunciation explicit in an English-language context (see also romanization of Hebrew), especially for Christians who may not use Hebrew regularly during prayer and study.

This short form of the name occurs 50 times in the text of the Hebrew Bible, of which 24 form part of the phrase "Hallelujah", a phrase that continues to be employed by Jews and Christians to give praise to Yahweh. In the Christian King James Version (1611) there is a single instance of JAH (capitalized), in Psalm 68:4. An American Translation (1939) and the New King James Version "NKJV" (1982) follows KJV in using Yah in this verse.

While pronouncing the tetragrammaton is forbidden for Jews, articulating "Jah"/"Yah" is allowed, but is usually confined to prayer and study.

The name Jah is frequently employed by adherents of Rastafari to refer to God.