Piece of seating furniture comprising: a base; and a seating unit; wherein - between the base and the seating unit a rotary bearing comprising a base-side bearing device and a seating-unit-side bearing device is provided, by means of which the seating unit is rotatable about a vertical axis relative to the base; - the rotary bearing has a switchable blocking device by means of which rotatability of the bearing devices (32, 34) with respect to one another is blockable; - the blocking device is configured for form-fitting coupling of the bearing devices and for this purpose has two profiles (50a, 50b) comprising an inner profile, which is attached to one of the bearing devices (32, 34) in a rotationally fixed manner, and an outer profile which is attached to the other one of the bearing devices (32, 34) in a rotationally fixed manner; and - the outer profile and the inner profile are displaceable with respect to one another in a direction of the vertical axis such that they are axially movable between an engaging relative position rotationally coupled in a form-fitting manner and a releasing relative position; characterized in that the piece of seating furniture has a stand-assistance function by way of which a seating surface can be raised, wherein the blocking device is operatively coupled to the stand-up assistance function such that when the stand-up assistance function is actuated, the blocking device takes up its blocked state. a base; and a seating unit; wherein - between the base and the seating unit a rotary bearing comprising a base-side bearing device and a seating-unit-side bearing device is provided, by means of which the seating unit is rotatable about a vertical axis relative to the base; - the rotary bearing has a switchable blocking device by means of which rotatability of the bearing devices (32, 34) with respect to one another is blockable; - the blocking device is configured for form-fitting coupling of the bearing devices and for this purpose has two profiles (50a, 50b) comprising an inner profile, which is attached to one of the bearing devices (32, 34) in a rotationally fixed manner, and an outer profile which is attached to the other one of the bearing devices (32, 34) in a rotationally fixed manner; and - the outer profile and the inner profile are displaceable with respect to one another in a direction of the vertical axis such that they are axially movable between an engaging relative position rotationally coupled in a form-fitting manner and a releasing relative position; - between the base and the seating unit a rotary bearing comprising a base-side bearing device and a seating-unit-side bearing device is provided, by means of which the seating unit is rotatable about a vertical axis relative to the base; - the rotary bearing has a switchable blocking device by means of which rotatability of the bearing devices (32, 34) with respect to one another is blockable; - the blocking device is configured for form-fitting coupling of the bearing devices and for this purpose has two profiles (50a, 50b) comprising an inner profile, which is attached to one of the bearing devices (32, 34) in a rotationally fixed manner, and an outer profile which is attached to the other one of the bearing devices (32, 34) in a rotationally fixed manner; and - the outer profile and the inner profile are displaceable with respect to one another in a direction of the vertical axis such that they are axially movable between an engaging relative position rotationally coupled in a form-fitting manner and a releasing relative position; characterized in that the piece of seating furniture has a stand-assistance function by way of which a seating surface can be raised, wherein the blocking device is operatively coupled to the stand-up assistance function such that when the stand-up assistance function is actuated, the blocking device takes up its blocked state.