B (named bee /ˈbiː/) is the second letter in the ISO basic Latin alphabet. It is used to represent a variety of bilabial sounds (depending on language), most commonly a voiced bilabial plosive.

⟨B⟩ may have started as a pictogram of the floorplan of a house in Egyptian hieroglyphs. By 1050 BC, the Phoenician alphabet's letter had a linear form that served as the beth.

The modern lowercase ⟨b⟩ derives from later Roman times, when scribes began omitting the upper loop of the capital.

In English, most other languages that use the Latin alphabet, and the International Phonetic Alphabet, ⟨b⟩ denotes the voiced bilabial plosive /b/, as in bib. In English it is sometimes silent; most instances are derived from old monosyllablic words with the b final and immediately preceded by an m, such as lamb and bomb; a few are examples of etymological spelling to make the word more like its Latin original, such as debt or doubt.

In Estonian, Icelandic, and Chinese pinyin, ⟨b⟩ does not denote a voiced consonant; instead, it represents a voiceless /p/ that contrasts with either a geminated /pp/ (in Estonian) or an aspirated /pʰ/ (in Chinese, Danish and Icelandic), represented by ⟨p⟩. In Fijian ⟨b⟩ represents a prenasalized /mb/, whereas in Zulu and Xhosa it represents an implosive /ɓ/, in contrast to the digraph ⟨bh⟩ which represents /b/.