Sol (The Sun) was formed approximately 5 billion years ago out of a slowly condensing cloud of debris and gas, probably left over from previous supernovae. It is a main sequence star of the spectral class G2 and will at least shine for another 5 billion years.

The Solar System consists of the Sol and the other celestial objects gravitationally bound to it: the eight planets, their 166 known moons,three dwarf planets (Ceres, Pluto, and Eris and their four known moons), and billions of small bodies. This last category includes asteroids, Kuiper belt objects, comets, meteoroids, and interplanetary dust. In broad terms, the the Solar System consist of the Sun, four terrestrial inner planets, an asteroid belt composed of small rocky bodies, four gas giant outer planets, and a second belt, called the Kuiper belt, composed of icy objects. Beyond the Kuiper belt lies the scattered disc, the heliopause, and ultimately the hypothetical Oort cloud.

In order of their distances from the Sun, the planets are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. Six of the eight planets are in turn orbited by natural satellites, usually termed "moons" after Earth's Moon, and each of the outer planets is encircled by planetary rings of dust and other particles.

Most large objects in orbit around the Sun lie near the plane of Earth's orbit, known as the ecliptic. The planets are very close to the ecliptic while comets and Kuiper belt objects (such as Pluto) are usually at significantly greater angles to it.

The direction of all the planets' revolution in their orbits around the Sun is the same as that of the Sun's rotation on its axis, namely counter-clockwise as viewed from Earth's north.

All of the planets and most other objects also orbit with the Sun's rotation in a counter-clockwise direction as viewed from a point above the Sun's north pole. There are exceptions, such as as three planets - Venus, Uranus, and Pluto. The slow spin of Venus is opposite (retrograde) to that of the Sun and the other planets. Uranus apparently lies on its side, with its poles almost in the plane of its orbit. The Pluto-Charon system also rotates almost on its side.

In Star Trek, the Solar system (or Terran system) is located in Sector 001, in the Alpha Quadrant and is very much at the heart of the United Federation of Planets (UFP), especially Earth. Earth was one of the founding members of the Federation (together with the Alpha Centaurians, Vulcans, Tellarites, and Andorians). The Federation Council has its headquarters in San Francisco and the Federation Council President its office in Paris, both in Earth. Starfleet Headquarters, is located in San Francisco, Terra, as is the main campus of Starfleet Academy, its training center.

Mars was colonised by humans in 2103. A Starfleet base was established at a vast lava plain on the planet, Utopia Planitia, along with the Utopia Planitia Fleet Yards in geo-synchrynous orbit above, where many famous vessels including the USS Enterprise-D and the USS Defiant were built. Mars was also an important part in the defense of the Sol system and the location of the Mars Defense Perimeter. (TOS: "Court Martial"; TNG: "The Best of Both Worlds"; Star Trek: The Next Generation Technical Manual)

Mars was the first planet to be terraformed by Humans. Colonists originally dwelt within domed cities while the verteron array was used to redirect comets and asteroids towards the Red Planet to impact in the polar caps. This freed carbon dioxide and released it into the atmosphere, increasing the planet's temperature and water volume. By 2155, conditions in the lowlands of the Martian surface were sufficiently altered to allow Humans to roam freely without heavy environmental suits. (ENT: "Demons")

Jupiter was home to Jupiter Station - a starbase in orbit of Jupiter which served as a repair facility to Starfleet. (ENT: "Silent Enemy", et al.)