3U

3U or 3-U may refer to:

• Sichuan Airlines's IATA code
• A type of Rack unit
• Zerstörergeschwader 26, from its historic Geschwaderkennung code with the Luftwaffe in World War II
• A CubeSat measuring 30×10×10 cm
• The acronym for the third (3rd) catalog of Uhuru x-ray sources

See also

• U3 (disambiguation)