A drainable ostomy pouch having sidewalls of flexible sheet material defining a cavity therebetween and a downwardly-extending neck portion terminating in a discharge opening that is closed by folding the neck portion upwardly and opened by unfolding the neck downwardly. Each of the sidewalls of the neck portion is provided with a transversely-extending bias member that is formed of stiff but flexible, spring-like plastic material. The bias members are normally flat so as to be in straight parallel closed condition but are openable under inwardly-directed finger pressure applied to their opposite ends to cause them to bow outwardly away from each other. The pouch also includes a two-part fastening system for holding the neck portion in upwardly-folded condition, the system including a first fastener part located along the outer surface of one of the sidewalls of the neck portion and a second fastener part located along the outer surface of the other sidewall of the neck portion, the fastener parts having outwardly-projecting interengageable locking elements that are brought into interlocking engagement when the neck portion is fully folded.