Jonas Hesselman (1877 – 1957), was a Swedish engineer. He built the first spark ignition engine with direct injection of fuel into the cylinder.
Hesselman worked from 1899 to 1916 for AB Diesel Engines (later Atlas Diesel, now Atlas Copco) in Sickla in Nacka just outside Stockholm, from 1901 as Head of Construction. Here he also developed Rudolf Diesel's engine further and won international recognition as an authority on diesel engines. In 1916 he opened his own factory and in 1925 presented the Hesselman engine, a hybrid between an Otto engine and diesel engine.
Jonas Hesselman also designed electrical vehicle components, among others, the motor that became the basis for Hesselman Elhydraulik, now Haldex Hydraulics. In 1970, Hesselman Elhydraulik developed the hydraulic power unit that still serves as the prototype for the existing lifts for trucks.
He was elected a member of the Royal Swedish Academy of Sciences in 1934.