Hercules is a constellation named after Hercules, the Roman mythology hero adapted from the Greek hero Heracles. Hercules was one of the 48 constellations listed by the second-century astronomer Ptolemy, and it remains one of the 88 modern constellations today. It is the fifth-largest of the modern constellations and is the largest of the 50 which have no stars brighter than apparent magnitude +2.5.

Hercules is bordered by Draco to the north; Boötes, Corona Borealis, and Serpens Caput to the west; Ophiuchus to the south; Aquila to the southwest; and Sagitta, Vulpecula, and Lyra to the east. Covering 1225.1 square degrees and 2.970% of the night sky, it ranks fifth among the 88 constellations in size. The three-letter abbreviation for the constellation, as adopted by the International Astronomical Union in 1922, is 'Her'. The official constellation boundaries, as set by Eugène Delporte in 1930, are defined by a polygon of 32 segments (illustrated in infobox). In the equatorial coordinate system, epoch 2000, the right ascension coordinates of these borders lie between 16^h 00^m 26.64^s and 18^h 57^m 49.50^s, while the declination coordinates are between +3.67° and +51.32°. In mid-northern latitudes, Hercules is best observed from mid-spring until early autumn, culminating at midnight on June 13.

The solar apex is the direction of the open motion with respect to the Local Standard of Rest. This is located within the constellation of Hercules, around coordinates right ascension 18^h 00^m and declination 30° 00′. The north pole of the supergalactic coordinate system is located within this constellation at right ascension 18^h 55^m 01^s and declination +15° 42′ 32″.

Hercules has no first or second magnitude stars. However, it does have several stars above magnitude 4. Alpha Herculis, traditionally called Rasalgethi, is a triple star system, partly resolvable in small amateur telescopes, 359 light-years from Earth. Its common name means "the kneeler's head". The primary is an irregular variable star; it is a bright giant with a minimum magnitude of 4 and a maximum magnitude of 3. It has a diameter of roughly 400 solar diameters. The secondary, a spectroscopic binary that orbits the primary every 3600 years, is a blue-green hued star of magnitude 5.6. Beta Herculis, also called Kornephoros, is the brightest star in Hercules. It is a yellow giant of magnitude 2.8, 148 light-years from Earth; kornephoros means club-bearer. Delta Herculis A is a double star divisible in small amateur telescopes. The primary is a blue-white star of magnitude 3.1, and is 78 light-years from Earth. The optical companion is of magnitude 8.2. Gamma Herculis is also a double star divisible in small amateur telescopes. The primary is a white giant of magnitude 3.8, 195 light-years from Earth. The optical companion, widely separated, is 10th magnitude. Zeta Herculis is a binary star that is becoming divisible in medium-aperture amateur telescopes, as the components widen to their peak in 2025. The system, 35 light-years from Earth, has a period of 34.5 years. The primary is a yellow-tinged star of magnitude 2.9 and the secondary is an orange star of magnitude 5.7.

Hercules hosts further quite bright double stars and binary stars. Kappa Herculis is a double star divisible in small amateur telescopes. The primary is a yellow giant of magnitude 5.0, 388 light-years from Earth; the secondary is an orange giant of magnitude 6.3, 470 light-years from Earth. Rho Herculis is a binary star 402 light-years from Earth, divisible in small amateur telescopes. Both components are blue-green giant stars; the primary is magnitude 4.5 and the secondary is magnitude 5.5. 95 Herculis is a binary star divisible in small telescopes, 470 light-years from Earth. The primary is a silvery giant of magnitude 4.9, and the secondary is an old, reddish giant star of magnitude 5.2. The star HD164669 near the primary may be an optical double. 100 Herculis is a double star easily divisible in small amateur telescopes. Both components are magnitude 5.8 blue-white stars; they are 165 and 230 light-years from Earth.

There are several dimmer variable stars in Hercules. 30 Herculis, also called g Herculis, is a semiregular red giant with a period of 3 months. 361 light-years from Earth, it has a minimum magnitude of 6.3 and a maximum magnitude of 4.3. 68 Herculis, also called u Herculis, is a Beta Lyrae-type eclipsing binary star. 865 light-years from Earth, it has a period of 2 days; its minimum magnitude is 5.4 and its maximum magnitude is 4.7.

Mu Herculis is 27.4 light-years from Earth. The solar apex, i.e., the point on the sky which marks the direction that the Sun is moving in its orbit around the center of the Milky Way, narrowly figures in Hercules, between Hercules' left elbow (near Omicron Herculis) and Vega (in neighboring Lyra).

Fifteen stars in Hercules are known to be orbited by extrasolar planets.