The 2022 Giro champion climbed into an ambulance after sitting on the pavement for several minutes following a crash that occurred around 70 kilometres from the finish in Naples.
On roads made very slippery by rain, many riders fell including Ecuadorian Richard Carapaz, winner of the 2019 Giro, Frenchman Paul Magnier and Briton Adam Yates.
Hindley was the hardest hit and, despite being able to get up on his own, was forced to abandon, depriving Red Bull Bora teammate Primoz Roglic of an important ally in the mountains.
German rider Juri Hollmann was also forced to pull out with a suspected fractured arm, according to his team, Alpecin.
After the crash, the stage was neutralised and the riders continued to move forward at a slower pace for around twenty kilometres before a new start was given and racing resumed towards the finish in Naples.
The organisers then announced all the riders would be classified in the same time and no bonuses would be awarded at the finish.