U with double acute is only used in the Chuvash language, where it represents the close front rounded vowel/y/, the pronunciation of the Latin letter U with umlaut (Ü ü) in German. It is placed between ⟨У⟩ and ⟨Ф⟩ in the Chuvash alphabet. It is usually romanized as ⟨Ü⟩ but its ISO 9 transliteration is ⟨Ű⟩.
It was also formerly used in the Altai alphabet of 1840.