Yo (Ё, ё) is the seventh letter of the Cyrillic alphabet. It is used in the Russian and Belarusian languages, along with many of the Caucasian and Turkic languages which use or used the Cyrillic alphabet, but not in many of the other Slavic languages. This article will focus on its use in Russian.

It is spoken as an iotated or palatalized O ("yo", IPA [jo]), but when following a postalveolar fricative, like ж, ч, ш and щ, is pronounced simply as [o].

Yo is identical in form to ye, as well as Latin E, except for a symbol similar to an umlaut or diaresis. This diacritic serves no regular function in Russian (as it does in German or French), and is added only to differentiate this letter from ye.

Though in common use after WWII, yo is disappearing in printed Russian, replaced by the letter ye due to their similar appearance. It is still used in children's books and textbooks for foreign learners, and is used idiosyncratically in handwriting.

The fact that yo is frequently replaced with ye in print often causes some confusion to non-Russians, as it makes Russian words and names harder to transcribe accurately. One recurring problem is with Russian surnames, as both -ев(-ev) and -ёв(-ov) are common endings. Thus the English-speaking world knows two leaders of the former Soviet Union as Khrushchev and Gorbachev though their surnames end in Russian with -ёв, better transcribed ov.

In Belarusian it is considered improper to replace "yo" with "ye".

See also: E (Cyrillic), O (Cyrillic), Epsilon (letter), E, Reforms of Russian orthography.