Ice XV is a crystalline form of ice, the proton-ordered form of ice VI. It is created by cooling water to around 130 K at 1 GPa (9820 atm).
Ordinary water ice is known as ice Ih, (in the Bridgman nomenclature). Different types of ice, from ice II to ice XV, have been created in the laboratory at different temperatures and pressures.
On 14 June, 2009, Christoph Salzmann at the University of Oxford and colleagues reported having created ice XV and say that its properties differ significantly from those predicted. In particular, ice XV is antiferroelectric rather than ferroelectric as had been predicted.
In fiction 
Ice-fifteen is mentioned in Terminal Freeze, a novel by Lincoln Child.
See also 
- Ice for other crystalline form of ice
- Chaplin, Martin (2007-11-11). "Ice-six structure". Water Structure and Science. Retrieved 2008-01-02.