The Lanz Bulldog was a tractor manufactured by Heinrich Lanz AG in Mannheim, Baden-Württemberg, Germany. Production started in 1921 and various versions of the Bulldog were produced up to 1960, one of them being the Lanz Bulldog D 9506. John Deere purchased Lanz in 1956 and started using the name "John Deere Lanz" for the Lanz product line. A few years after the Bulldog was discontinued the Lanz name fell into disuse. The Lanz Bulldog was one of the most popular German tractors, with over 220,000 of them produced in its long production life. The name "Bulldog" is widely used in Germany as a synonym for tractors even today, especially in Bavaria.

The Bulldog was a simple and easily maintained vehicle due primarily to its simple, single cylinder, horizontal, two-stroke, hot bulb engine. Initially the engine was a 6.3 litre, 12 horsepower unit, but as the Bulldog evolved the engine was increased to 10.3 litres and 55 horsepower. While hot bulb engines were crude, they were easy to maintain and could burn a wide variety of low grade fuels – even waste oils. The engine was designed by Fritz Huber.

The Bulldog design was copied in other countries by several different manufacturers. While some of these copies were legitimately produced under license from Bulldog, most of them were built with each respective builder's own frame and body design, being powered by unlicensed copies of the patented Bulldog hot-bulb engine. Some of these examples are