A beverage container lid comprising a body having drinking hole and an air hole, and a slide-seal automatic Open and Close retention mechanism that comprises a sealing arm pivotally connected to the body, a movement and position retention linkage structured and operable to move the sealing arm between an Opened and a Closed position, a control mechanism slidingly disposed within the body and operably connected to the movement and position retention linkage such that movement of the control mechanism will control movement of the sealing arm between the Opened and Closed positions, and a biasing device structured and operable to exert constant force on the sealing arm, such that force exerted by the biasing device in combination with the structure and operation of the movement and position retention linkage will selectively retain the sealing arm in the Opened position and in the Closed position.