The German from Bora-Hansgrohe got the better of Elia Viviani (Deceuninck-QuickStep) and Caleb Ewan (Lotto-Soudal) as he burst through the middle to stop the clock on 4:44:43 after 205km of racing on a largely flat course from Bologna.
“I’m just so happy. It was my first chance to win a stage and we did it straight.
“I think the team is now more and more motivated and it is good for the next three weeks.”
Ackermann, who admitted to feeling some pre-race pressure to deliver for the team, said he decided to open up his sprint with 250m to go.
“I decided I have to take my speed and go full gas and luckily it was enough.
“It was pressure, but you also have to know that it is my first Grand Tour and you never know what will happen in your first Grand Tour and I’m just happy to have won my first stage.”
The peloton reeled in a breakaway group of four riders some 7km from the finish.
The quartet – Francois Bidard (AG2R La Mondiale), Lukasz Owsian (CCC Team), Marco Frapporti (Androni Giocattoli-Sidermec) and Giulio Ciccone (Trek-Segafredo) – were part of an initial group of eight that led the stage for more than 190km and built a maximum advantage of 4:40.
Monday’s third stage will be contested over 220km from Vinci to Orbetello.