Abstract: A spill-proof cup assembly is disclosed as including a cup with an open end, a cover for covering the open end of the cup to define a cavity for containing a liquid, the cover having a drinking spout, a vent, and support columns leading from the drinking spout towards the cavity, and a flow control mechanism engageable with the cover, and the flow control mechanism includes a first valve membrane and a second valve membrane, in which the first valve member includes an edge which is movable, when the flow control mechanism is engaged with the cover, between a first position in which the edge is in abutment with an interior surface of the cover to prevent fluid communication through the vent into the cavity, and a second position in which the edge of the first valve member is out of abutment with the interior surface of the cover to allow fluid communication through the vent into the cavity, and the second valve membrane is movable between a first position in which a generally convex surface of the second valve