The Land Rover Series I, II, and III , or simply the Land-Rover (commonly referred to as Series Land Rovers, to distinguish them from later models) are compact British off-road vehicles, produced by the Rover Company since 1948, and later by British Leyland. Inspired by the World War II jeep, it was the first mass-produced civilian four-wheel drive car with doors, and an available hard roof. Unlike conventional cars and trucks of the time, it used a sturdy fully box-welded frame. Furthermore, due to post-war steel shortage, and aluminium surplus, Land Rovers received non-rusting aluminium alloy bodies, favouring their longevity. In 1992, Land Rover claimed that 70% of all the vehicles they had built were still in use.

Most Series models feature leaf-spring suspension with selectable two or four-wheel drive (4WD), however Series I's produced between 1948 and mid-1951 had constant 4WD via a freewheel mechanism, and the Stage 1 V8 version of the Series III featured permanent 4WD. All three models could be started with a front hand crank and had the option of front & rear power takeoffs for accessories.

After adding a long wheelbase model in 1954, Land Rover also offered the world's first four / five door, 4WD off-road station wagon in 1956. Series Land Rovers and Defenders continually excelled in space utilization, offering (optional) three abreast seating in the seating rows with doors, and troop seating in the rear, resulting in up to seven seats in the SWB, and up to ten seats in the LWB models, exceeding the capacity of most minivans, when comparing vehicles of the same length.

The Land Rover was conceived by the Rover Company in 1947 during the aftermath of World War II. Before the war, Rover had produced luxury cars which were not in demand in the immediate post-war period and raw materials were strictly rationed to those companies building construction or industrial equipment, or products that could be widely exported to earn crucial foreign exchange for the country. Also, Rover's original factory in Coventry had been bombed during the war, forcing the company to move into a huge "shadow factory" built just before the war in Solihull near Birmingham, previously used to construct Bristol Hercules aircraft engines. This factory was now empty but starting car production there from scratch would not be financially viable. Plans for a small, economical car known as the M Type were drawn up, and a few prototypes made, but would be too expensive to produce.

Maurice Wilks, Rover's chief designer came up with a plan to produce a light agricultural and utility vehicle, of a similar concept to the Willys Jeep used in the war, but with an emphasis on agricultural use. He was possibly inspired by the Standard Motor Company, who faced similar problems and were producing the highly successful Ferguson TE20 tractor in their shadow factory in Coventry. More likely, he used his own experience of using an army-surplus Jeep on his farm in Anglesey, North Wales. His design added a power take-off (PTO) feature since there was a gap in the market between jeeps and tractors (which offered the feature but were less flexible as transport). The original Land Rover concept (a cross between a light truck and a tractor) is similar to the Unimog, which was developed in Germany during this period.

The first prototype had a distinctive feature – the steering wheel was mounted in the middle of the vehicle. It hence became known as the "centre steer". It was built on a Jeep chassis and used the engine and gearbox out of a Rover P3 saloon car. The bodywork was handmade out of an aluminium/magnesium alloy called Birmabright, to save on steel, which was closely rationed. The choice of colour was dictated by military surplus supplies of aircraft cockpit paint, so early vehicles only came in various shades of light green. The first pre-production Land Rovers were being developed in late 1947 by a team led by engineer Arthur Goddard.

Tests showed this prototype vehicle to be a capable and versatile machine. The PTO drives from the front of the engine and from the gearbox to the centre and rear of the vehicle allowed it to drive farm machinery, exactly as a tractor would. It was also tested ploughing and performing other agricultural tasks. However, as the vehicle was readied for production, this emphasis on tractor-like usage decreased and the centre steering proved impractical in use. The steering wheel was mounted off to the side as normal, the bodywork was simplified to reduce production time and costs and a larger engine was fitted, together with a specially designed transfer gearbox to replace the Jeep unit. The result was a vehicle that didn't use a single Jeep component and was slightly shorter than its American inspiration, but wider, heavier, faster and still retained the PTO drives.

The Land Rover was designed to only be in production for two or three years to gain some cash flow and export orders for the Rover Company so it could restart up-market car production. Once car production restarted, however, it was greatly outsold by the off-road Land Rover, which developed into its own brand that remains successful today. Many of the defining and successful features of the Land Rover design were in fact the result of Rover's drive to simplify the tooling required for the vehicle and to use the minimum amount of rationed materials. As well as the aluminium alloy bodywork (which has been retained throughout production despite it now being more expensive than a conventional steel body due to its ideal properties of light weight and corrosion resistance) other examples include the distinctive flat body panels with only simple, constant-radius curves (originally used because they could be cut and formed by hand from aluminium sheet on a basic jig) and the sturdy box-section ladder chassis, which on series vehicles was made up from four strips of steel welded at each side to form a box, thus cutting down on the complex operations required when making a more conventional U- or I-section frame.