The SNECMA-Régnier 4L is a French four cylinder air-cooled inverted inline piston engine, introduced shortly after the end of World War II.

Though they remained influenced by de Havilland practice their products began to diverge and eventually contained original designs.

[1][2] By the mid-1930s they had several four cylinder air-cooled inverted inline engines on offer, including the R.4L-02 displayed at the 1936 Paris Air Show.

[4] During the Occupation of France and in the years shortly after World War II, Régnier designed and produced a set of three simplified four-cylinder inverted air-cooled inline engines of increasing capacity and power, the 4J, 4K and 4L.

Notable constructional features, shared with the 4J and 4K engines,[5] included machined steel cylinder barrels with external baked-on anti-corrosion varnish and separate cylinder heads with unusual metallo-plastic seals, held to the crankcase by long bolts.