8.8 cm Flak 18

8.8 cm Flak 18-36
8.8 cm Flak 18 barrel on a Flak 36 cruciform at the Imperial War Museum in London
Type	Anti-aircraft gun
Place of origin	Nazi Germany
Service history
In service	1936–1945
Used by	Nazi Germany Spain Finland Greece Soviet Union United States Republic of China Brazil
Wars	Spanish Civil War, Sino-Japanese War, World War II
Production history
Designer	Krupp
Designed	1928
Manufacturer	Krupp, Rheinmetall
Unit cost	33,600 RM
Produced	1933–45
No. built	21,310
Specifications (Flak 36)
Weight	7,407 kg (16,325 lbs) in mounted position
Length	5.791 m (20 ft)
Barrel length	4.938 m (16 ft 2 in) L/56 (56 calibers)
Height	2.10 m (6 ft 11 in) (firing)
Shell	88 × 571 mm. R
Caliber	88 mm (3.46 in)
Barrels	One, 32 grooves with right-hand increasing twist from 1/45 to 1/30
Breech	Horizontal semi-automatic sliding block
Recoil	Independent liquid and hydropneumatic
Carriage	Sonderanhänger 202
Elevation	-3° to +85°
Traverse	360°
Rate of fire	15–20 rpm
Muzzle velocity	840 m/s (2,690 ft/s)
Effective firing range	14,860 m (16,250 yds) ground target 8000 m (26,240 ft) effective ceiling
Maximum firing range	9900 m (32,500 ft) maximum ceiling
Sights	ZF.20

The 8.8 cm Flak 18/36/37/41 (commonly called the eighty-eight) was a German 88 mm anti-aircraft and anti-tank artillery gun from World War II. It was widely used by Germany throughout the war, and was one of the most recognized German weapons of that conflict. Development of the original model led to a wide variety of guns.

The name applies to a series of related guns, the first one officially called the 8.8 cm Flak 18, the improved 8.8 cm Flak 36, and later the 8.8 cm Flak 37. Flak is a contraction of German Flugzeugabwehrkanone meaning "aircraft-defense cannon", the original purpose of the eighty-eight. In English, "" became a generic term for ground anti-aircraft fire. In informal German use, the guns were universally known as the Acht-acht ("eight-eight").

The versatile carriage allowed the eighty-eight to be fired in a limited anti-tank mode when still on its wheels; it could be completely emplaced in only two-and-a-half minutes. Its successful use as an improvised anti-tank gun led to the development of a tank gun based upon it: the 8.8 cm KwK 36, with the "KwK" abbreviation standing for Kampfwagen-Kanone (literally "battle vehicle cannon", or "main battle tank cannon"), meant to be placed in a gun turret as the tank's primary armament. This gun served as the main armament of the Tiger I heavy tank.

In addition to these Krupp designs, Rheinmetall later created a more powerful anti-aircraft gun, the 8.8 cm Flak 41, which was produced in relatively small numbers. Krupp responded with another prototype of the long-barreled 88 mm gun, which was further developed into the anti-tank and tank destroyer 8.8 cm PaK 43 gun used for the Elefant and Jagdpanther, and turret-mounted 8.8 cm KwK 43 heavy tank gun of the Tiger II.