The Tatra 815 is a truck family, produced by Czech company Tatra. It uses the traditional Tatra concept of rigid backbone tube and swinging half-axles giving independent suspension. The vehicles are available in 4x4, 6x6, 8x8, 10x8, 10x10, 12x8 and 12x12 variants. There are both air-cooled and liquid-cooled engines available with power ranging from 230–440 kilowatts (310–590 hp). As a successor to Tatra 813 it was originally designed for extreme off-road conditions, while nowadays there are also variants designated for mixed (both off- and on-road) use. The gross weight is up to 35,500 kg (78,264 lb).

The 815 and its descendant models took the Czech truck racer Karel Loprais to victory six times in the Dakar Rally.

Designed to eventually replace the Tatra 148, the prototype Tatra 157 was introduced in 1970 and several more prototypes were designed between 1970 and 1974 period but no production resulted. Due to protests from another Czechoslovak manufacturer LIAZ which was assigned by the government central planning committee to manufacture trucks of similar class, Tatra dropped the 157 and instead started to concentrate on a heavier class as the replacement for the 813 and 148 which was introduced in 1983 as the 815 series. In 1989 Tatra modernized the 815 and introduced new 815-2 which received further upgrade in 1994 and just 3 years later in 1997 the new cabin TerrN°1 is introduced. Another facelift followed in 2000 where changes included among others new instrument panel and cab attachment and for the first time there is an option for fitment of liquid-cooled engines. The latest facelift of cabin came in July 2010. Due to emission requirements changes in 2003 Tatra developed all new V8 engine T3C to comply with Euro III where it followed the tradition once again with its air cooling design. The further developed T3D engine was introduced in 2006 with its SCR and Euro IV compliance.

Manufacturing ended on 25 February 2025 with 158,065 units made.

While most other manufacturers derive their trucks from road applications, the 815 was purposely designed for extreme off-road conditions, and its road versions are derived from the off-road original concept. The principle consists in a central load-carrying tube with independently suspended swinging half-axles bolted as one whole. This gives Tatra vehicles outstanding driving qualities in the most difficult terrains. The concept allows higher off-road speed compared to classical rigid axle design.

The primary structural feature of Tatra trucks is the central load carrying tube, also called a backbone frame. All other parts of the truck are mounted to this rigid assembly. The inherently high torsional and flexural rigidity of this layout protects superstructures from the motions and forces on the axles. Torque distribution to the axles is also carried within the backbone.

Tatra differentials are a unique design that uses two opposing spiral bevel gears instead of the usual single set. The differential gears are part of the input drive shaft rather than between the output axles as in a conventional differential. All versions of the Tatra differential have locking pins that can force the differential gears to rotate together, "locking" the differential. This arrangement had two distinct advantages. The first is that the dual output bevel gears allow the axles to swing around the drive axle without the need for universal couplings. The second is that the input drive shaft goes essentially straight through the differential housing, allowing simple coupling to a second set of swing axles. This modular design enables configurations of 2, 3, 4, 5, or even 6 axles with all axles driven. The whole assembly is part of the backbone frame.

All suspension types are equipped with telescopic shock absorbers; some versions also have stabilizer torsion bars.