The letter Ou () is a letter in the extended Latin alphabet.

The letter was invented by Christian missionaries, originally for writing the Wendat language. It was based on a non-standard ligature from the Greek alphabet for ου. In Cyrillic this ligature spawned a shorter form of the letter Uk, which was previously written as a ligature of О and У (Ѹ, ѹ).

Today, Ou is used for writing the Algonquin language.

In Unicode it is in the Latin Extended-B range at code points U+0222 (uppercase) and U+0223 (lowercase). In older character encodings (such as ISO 8859) and locales where Unicode is not available, it is usually represented by an italic 8 glyph.