HL is an abbreviation for:
- Half-life, radioactive decay
- Half-Life (series), a video game series
- Half-Life (video game), the first game in that series
- Hangars Liquides, an electronic music label
- Headline
- Hypotenuse Leg, a condition of congruence in right angles
- Hectolitre, 100 liters (as hl or hL)
- Herman Li, guitarist for the power metal band DragonForce
- Higher Level, a level of course difficulty in the International Baccalaureate Diploma Programme
- Hit list (disambiguation)
- Hitachi-LG Data Storage (also abbreviated HL-DL-ST), a joint venture between Hitachi and LG, mainly producing optical disc drive
- Hotline
- Hodgkin's lymphoma, a highly treatable hematological malignancy ("blood cancer")
- Hospitality Lawyer, a hospitality resource website founded by Stephen Barth
- Houlihan Lokey, a leading international investment bank
- House of Lords
- Hovedstadens Lokalbaner, a Danish local railway company
- South Korea (amateur radio call sign prefix assigned to the country)
- Horseland
- Hydrogen line
- Highlighter
- Voiceless alveolar lateral fricative (frequently written as "hl" or "ɬ")
- Hugh Laurie, actor
- Hargreaves Lansdown, British investment company
Miscellaneous:
- hl is the label of an argument in Google web addresses specifying the interface language ('host language') the Google web page should be in.