Andromeda was the daughter of Cepheus and Cassiopeia who boasted herself to be more beautiful than the Nereid sea-maidens. Poseidon the sea-god sent a monster as a punishment, that would only be placated by the sacrifice of Andromeda herself. Perseus came to her rescue and, with the aid of Medusa's head, turned the ravaging beast to stone.

The stars of Andromeda are in general fairly faint. The brightest is the Beta star, Mirach, with a variable magnitude that can reach nearly +2.0. Two other stars come very close to this brightness: Alpha Andromedae or Sirrah (also called Alpheratz) was originally part of the neighbouring constellation of Pegasus. Together with Alamak, these three form a nearly straight line that defines the shape of the constellation.

Much fainter than any of these is a star five degrees from Alamak, designated Upsilon Andromedae. About forty-four light years from Earth, this star is known to have three planets in orbit, the first multiple-planet system discovered outside Earth's Solar System.

What Andromeda lacks in bright stars it more than compensates for in galaxies, and one galaxy in particular. In the central regions of the constellation is M31, much better known as the Andromeda Galaxy. This is a huge spiral galaxy about twice the size of our own, and a near neighbour in galactic terms. Nonetheless, its distance of 2,300,000 light years makes it the most distant object visible with the naked eye.

Aside from the famous galaxy, Andromeda contains a variety of notable objects. On the fringes of the Milky Way lies NGC 7662, descriptively referred to as the Blue Snowball Nebula. On the other side of the constellation is an open star cluster, NGC 752, 1,300 light years away and on the verge of naked eye visibility.