The latching gas ON/OFF assembly includes a housing with a female threaded bore for receiving a male threaded neck of a gas tank cylinder having a tank valve with a pin. A bonnet is slidably connected to the housing and slides between a forward OFF position and rearward ON position. A pin depressor connected to the bonnet with a transverse latch button for locking the bonnet in the ON position and for releasing the bonnet from the ON position. When the bonnet is slid to the rearward ON position it causes the pin depressor to contact the pin of the tank valve to permit gas to flow therefrom. The latching button is spring-biased toward a locked position where a plate on the free end thereof removably resides in a complementary seat in the housing.