Disclosed is a full movement jaw advancement oral appliance that is worn in the mouth of a user to reduce the effects of snoring and/or sleep apnea. The oral appliance includes an upper arch tray assembly against which the user's upper teeth carried are received, a lower arch tray assembly against which the user's lower teeth are received, and an intermediate guide post support tray that is connected at the bottom thereof to the lower arch tray assembly and at the top thereof to the upper arch tray assembly by an upper arch tray retaining post that extends therebetween. The upper arch tray assembly is movable in both horizontal and vertical directions relative to the lower arch tray assembly so that the positions of the user's upper and lower jaws can be adjusted relative to one another and the upper arch tray assembly will remain in receipt of the user's upper teeth when he opens his mouth during sleep.
