A beverage container closure or lid that is adapted for closing an open end of a beverage container. The lid is selectively couplable to the beverage container and includes a selectively openable stopper that when closed, creates a fluid-tight seal between the beverage container and the environment. The stopper may be selectively opened by a user when the user presses a button disposed on a side of the beverage container closure. The stopper is subsequently automatically closed when the user releases the button. Thus, a user may open and close the beverage container closure using a single hand without the need to remove the beverage container closure from the beverage container.