IV may refer to:

• The Roman number for 4 (number). There are also separate Unicode characters for this number, 0x2163 "" and 0x2173 "ⅳ").
• Côte d'Ivoire: NATO country code; from Ivory Coast.
• InterVarsity Christian Fellowship: A Christian ministry for college students.
• "Inter vivos": In law, as in inter vivos trust.
• Intravenous: In medicine, as in "IV drip" (or simply "IV") for intravenous drip, or "IV drug use" for intravenous drug use.
• Isla Vista: An unincorporated community near the Santa Barbara campus of the University of California, home to thousands of UCSB students.
• Instrumental variable, a statistical analysis method
• I've: In instant messaging slang, a shortened version.
• Led Zeppelin IV: Possibly Led Zeppelin's most famous album, containing the song, "Stairway to Heaven."
• IV (Cypress Hill album): The fourth album of west coast rap band Cypress Hill.
• IV (Godsmack album): The title of Godsmack's fourth album.
• IV, shortform for Industrievereinigung Federation of Austrian Industry.
• Subdominant scale degree, chord, or diatonic function: In music, when distinguished IV = major and iv = minor.
• Current-voltage: In electronics where current is given the symbol I and voltage is given the symbol V.
• Initialization vector: In encryption, a nonsecret binary vector used as the initializing input algorithm for the encryption of a plaintext block sequence to increase security by introducing additional cryptographic variance and to synchronize cryptographic equipment.

IV | Iv | IV | IV