U20
U20 or U-20 may refer to:

Naval vessels 
 
 , a sloop of the Royal Navy
 , a submarine of the Austro-Hungarian Navy

Other uses 
 Great truncated cuboctahedron
 Meizu U20, a smartphone
 Roland U-20, a synthesizer
 Small nucleolar RNA SNORD20
 U20 summit, an international summit for cities from the G-20 countries
 Under-20 athletics
 Uppland Runic Inscription 20