Their demands include an end to solitary confinement and to “administrative detention,” which allows Israel to detain them indefinitely without trial.
Israel is notorious for its policies of administrative detention and imprisoning children for offences as minor as throwing rocks at military cars.
The hunger strike has widespread support, and rallies were set to take place in several Palestinian cities.
It was called by the Fatah party, which governs in the West Bank, and is supported by resistance groups such as Hamas.
But Israel looks prepared to launch a brutal crackdown.
Israeli security minister Gilad Erdan has told jailers to “act in any way to contain the strike within the walls of the prisons and the Israeli police to provide any assitance needed.”
Erdan is also said to have ordered setting up a massive military hospital where hunger-striking prisoners could be force fed.