51 Andromedae (abbreviated 51 And) is the 5th brighest (4th magnitude) star in the constellation Andromeda. 51 Andromedae is the Flamsteed designation. It is occasionally called by the proper name Nembus in Bayer's Uranometria (1603) and Bode's star atlas Uranographia (1801).
Ptolemy included this star in Andromeda in the Almagest, but it was moved into Perseus by Johann Bayer, who designated it Upsilon Persei (υ Per). Flamsteed moved it back, and the International Astronomical Union made Flamsteed's 51 Andromedae its official designation in 1930.
In Chinese, 天大將軍 (Tiān Dà Jiāng Jūn), meaning Heaven's Great General, refers to an asterism consisting of 51 Andromedae, γ Andromedae, φ Persei, 49 Andromedae, χ Andromedae, υ Andromedae, τ Andromedae, 56 Andromedae, β Trianguli, γ Trianguli and δ Trianguli. Consequently, 51 Andromedae itself is known as 天大將軍三 (Tiān Dà Jiāng Jūn sān, English: the Third Star of Heaven's Great General.)
51 Andromedae is an orange K-type giant with an apparent magnitude of +3.59. It is approximately 177 light years from the Earth.