Istanbul LGBTI+ Pride Committee tweeted they would march Sunday afternoon in the city's Taksim neighborhood.
Organizers say in a statement that the governor banned the march "unlawfully" for the fourth year in a row. They say the ban violates their freedom of assembly and have vowed to march.
Since 2015, the governor has cited security reasons and public "sensitivities" as grounds for the ban. Prior to that, Turkish authorities allowed pride marches to take place for more than a decade since the first one in 2003. Up to 100,000 people attended Istanbul Pride in 2014.
Although homosexuality and transsexuality are not illegal in Turkey, LGBTI+ people face discrimination and hate crimes.