In the end, he came home with time to spare in a blistering run that is a personal and European best and came moments after compatriot Gianmarco Tamberi won gold in the high jump.
American Fred Kerley picked up the silver medal and Canadian Andre De Grasse took bronze.
It is the first time since the 2000 Olympics that the legendary Bolt has not been competing and few saw Jacobs as the man to inherit his title.
It led to one of the most open fields in recent history and there were shocks before the final with pre-games favourite Trayvon Bromell looking out of sorts and failing to qualify.
Great Britain’s Zharnel Hughes was disqualified for a false start.
Kerley (9.84) was the fastest athlete over the first 50 metres after a superb start from the former 400m runner.
However, the powerful Jacobs gathered speed as he moved into his stride, legs pumping to move past Kerley, who also set a personal best, as the line neared.
Andre de Grasse came through to take third, completing a podium of personal bests with a time of 9.89 ahead of Akani Simbine of South Africa.