Secondo Campini (August 28 1904 - February 7 1980) was an Italian engineer and one of the pioneers of the jet engine.

Campini was born at Bologna, Emilia-Romagna. In 1931 he wrote a proposal for the Italian Air Ministry on the value of jet propulsion and in 1932 demonstrated a jet-powered boat in Venice. With support of the Air Ministry, he began work with Italian aircraft manufacturer Caproni to develop a jet plane, the Campini Caproni CC.2, which first flew in 1940.

The "Thermojet" that Campini developed to propel this aircraft is substantially different from the jet engines of today. Campini's engine used an ordinary piston engine to compress air which was then mixed with fuel and ignited. Modern jets are based on the turbojet principle, but Campini's jet was nevertheless a true jet, since it was the reactive force of the burning exhaust gases that pushed the plane along.

After World War II, Campini emigrated to the US. Beginning in 1948, he worked on a number of military projects including the YB-49 flying-wing bomber.

He died in Milan in 1980.