FIM Sidecar World Championship is the international sidecar racing championship. It is the only remaining original FIM road racing championship class that started in 1949.

It was formerly named Superside when the sidecars moved from being part of Grand Prix Motorcycles racing to being support events for the Superbike World Championship. In 2010 the FIM took over the management of the series from the Superside promoters, and the championship was called "FIM Sidecar World Championship". However, the FIM still uses the word Superside for promotion purposes, despite the demise of the Superside promoters.

The championship is raced over a number of rounds at circuits mainly in Europe, although other venues have been included in United States (Monterey), South Africa at Kyalami and Australia's Phillip Island.

When the sidecar world championships began in 1949, they were dominated by unambiguous, orthodox outfits where a sidecar was attached to a conventional solo motorcycle. Rigidity and strength were poorly understood and pre-war machines have been described as "scaffolding on wheels". Development was based around cutting weight, providing a flat platform for the passenger, and reducing drag around the sidecar wheel and at the front of the sidecar platform. When developments in dolphin and dustbin fairings on solo machines proved successful at reducing drag, it was natural to adapt similar streamlined enclosures for the sidecar outfits. A pioneer in this area was Eric Oliver who worked with the Watsonian company on the development of successive experimental racing outfits including such innovations as the use of 16 in (410 mm) diameter wheels.

By 1953, motorcycle frames had undergone a complete redesign to accommodate the side car. Seat heights had been reduced to the point where the driver now sat in a semi-prone position. This permitted the use of a one-piece fairing which enclosed the front of the outfit as well as the sidecar platform. The enclosure led to unfamiliar handling, and the advanced design was only used in practice for the Belgian Grand Prix and in the final Grand Prix at Monza, where it finished fourth in the hands of Jacques Drion and Inge Stoll. Throughout the year, other outfits experimented with more modest refinements such as additional braking via the sidecar wheel, sometimes linked to one or both of the other two brakes.

Nevertheless, racing sidecars remained intrinsically the same to road-going sidecars. A traditional racing outfit was a road-going motorcycle outfit without the boot and with the suspension lowered. The bootless sidecar frame would have a flat platform. Both the battery and the fuel tank could be placed either between the motorcycle and the sidecar, or on the sidecar platform. Over time the subframe, struts, clamps, sidecar frame, etc. would merge with the motorcycle mainframe and form a single frame. But essentially the racing outfit was still a variant of the road-going outfit in principle.

Beginning in 1977 there was a seismic shift away from the traditional engineering that had underscored sidecar technology up to this point. It began when George O'Dell won the championship using a Hub-center steering sidecar (built by Rolf Biland) called the Seymaz. O'Dell won despite the Seymaz being rarely raced during the season in favor of using a traditional Windle frame for much of the year. The next year Rolf Biland won the 1978 championship using a BEO-Yamaha TZ500 sidecar which was basically a rear-engine, rear-drive trike.

In 1979 the FIM responded to these technological innovations by splitting the sidecar championship into two competitions: