摩羯座α（α Cap）是在摩羯座的一对光学双星。它的西方固有名称是Algiedi、Al Giedi、Algedi或Giedi，然而Giedi有时也会与摩羯座β相关联。

Algedi这个名称源自阿拉伯的الجدي al-jady这个字，意思是"小山羊"或"小朋友"，同时也是指整个摩羯座的范围。中文的名称是牛斗二，意思是星官牛斗的第二颗星。

两颗无关联的恒星系统构成了光学双星：

这两颗星在天空中相距0.11°，以裸眼就能分辨出来，类似于开阳和辅。

Alpha Capricorni (α Cap, α Capricorni) is an optical double star in the constellation Capricornus. It has the traditional names Algiedi, Al Giedi, Algedi or Giedi; however, Giedi is sometimes also associated with β Capricorni.

The name Algedi is derived from the Arabic word الجدي al-jady, meaning "the billy goat" or "kid," and also refers to the entire constellation of Capricornus. It is known as 牛宿二 (the Second Star of the Ox) in Chinese.