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Triangulum, which is Latin for "triangle," is one of the original 48 constellations listed by Greek astronomy Ptolemy in the 2nd century. It is named that way because the three brightest stars form a triangle although any three stars will form a triangle, that's just math.

It was known to the Babylonians as "The Plough," and its rising marked the time to begin ploughing the fields in Mesopotamia. To the Ancient Greeks, Triangulum was called "Deltoton," representing an upper-case Greek letter delta Δ. Others associated it with triangular landmarks, such as the Nile delta or the island of Sicily.

In order of brightness, the named stars are:

Alaybasan (β Trianguli), a binary star system about 141 light years from Earth. The system consists of two blue-white giant stars. Its name comes from the Arabic word Al-Aybasān meaning "the two joints."

Mothallah (α Trianguli) is a triple star system about 63 light years away. It consists of a yellow-white giant star and two red dwarf stars. Its name comes from the Arabic phrase raʼs al-muthallath meaning "the head of the triangle."

Apdu (γ Trianguli) is a solitary blue-white giant star about 112 light years from Earth. its name refers to an Ancient Egyptian constellation that was in the same area of the sky, Apdu, the Bird.

Deltoton (δ Trianguli) is a binary star system about 35 light years away. It consists of a yellow Sun-like star and a red dwarf. Its name refers to the original Ancient Greek name for Triangulum, Deltoton.

Triminus (ι Trianguli) is a quadruple star system about 289 light years away. It consists of at least two yellow giants and a yellow-white giant. Its name is an abbreviation of "Tri" for Triangulum and "minus" for Triangulum Minus, an obsolete constellation created by Polish astronomy Johannes Hevelius.