Microscopium ("the Microscope") is a minor constellation in the southern celestial hemisphere, one of twelve created in the 18th century by French astronomer Nicolas-Louis de Lacaille and one of several depicting scientific instruments.

The constellation's brightest star is Gamma Microscopii of apparent magnitude 4.68, a yellow giant 2.5 times the Sun's mass located 223 ± 8 light-years distant.

Nicknamed "Speedy Mic", BO Microscopii is a star with an extremely fast rotation period of 9 hours, 7 minutes.

Microscopium is a small constellation bordered by Capricornus to the north, Piscis Austrinus and Grus to the east, Sagittarius to the west, and Indus to the south, touching on Telescopium to the southwest.

[1] The official constellation boundaries, as set by Belgian astronomer Eugène Delporte in 1930, are defined by a polygon of four segments (illustrated in infobox).

Francis Baily considered Gamma and Epsilon Microscopii to belong to the neighbouring constellation Piscis Austrinus, but subsequent cartographers did not follow this.

Having spent much of its 620-million-year lifespan as a blue-white main sequence star, it has swollen and cooled to become a yellow giant of spectral type G6III, with a diameter ten times that of the Sun.

Both are white A-class magnetic spectrum variable stars with strong metallic lines, similar to Cor Caroli.

[20] An active star, it has prominent stellar flares that average 100 times stronger than those of the Sun, and are emitting energy mainly in the X-ray and ultraviolet bands of the spectrum.

[24] The Astronomical Society of Southern Africa in 2003 reported that observations of four of the Mira variables in Microscopium were very urgently needed as data on their light curves was incomplete.

[31] Describing Microscopium as "totally unremarkable", astronomer Patrick Moore concluded there was nothing of interest for amateur observers.

[33] NGC 6925 is a barred spiral galaxy of apparent magnitude 11.3 which is lens-shaped, as it lies almost edge-on to observers on Earth, 3.7 degrees west-northwest of Alpha Microscopii.

[41] Microscopium was introduced in 1751–52 by Lacaille with the French name le Microscope,[42][43] after he had observed and catalogued 10,000 southern stars during a two-year stay at the Cape of Good Hope.