Abstract: A mouthpiece for inhibiting breathing through a mouth of a user-wearer is disclosed herein. The mouthpiece for inhibiting breathing through a mouth of a user-wearer includes a blocking sheet, a relief port, and a flex recess. The blocking sheet may be made of a flexible material impermeable to air, and is configured to fit within the mouth of the user-wearer between the front teeth and the lips as well as the cheek area. The mouthpiece creates improved airflow for CPAP users by restricting airflow through the mouth.