An automatic deadbolt and combined latch and automatic deadbolt is disclosed whereby a manually operable control on the inside of a door may be used to enable and disable the automatic extension of the latch bolt to a comparable deadbolt position upon the closing of the door. This allows one not having a key to the lock to set the manual control and then leave a premises, whereby upon the closing of the door the latch bolt will automatically extend to a deadbolt position, being retractable therefrom to again open the door either by the use of a key from outside, or by rotation of the inner latch control to withdraw the latch. Withdrawing the latch to open the door resets the deadbolt function in the embodiment described so that upon subsequent reclosing of the door, the automatic deadbolt function will not be reactivated unless specifically called for by control of the inside side of the lock mechanism. In addition to the automatic deadbolt function, the latch may also be extended from its normal door latched position to the extended deadbolt position externally through the use of the normal lock key. An alternate embodiment in the form of an automatic deadbolt is also disclosed.