An ergonomically correct and size-adjustable pillow and/or travel pillow having an outer shell defining an internal perimetral channel that surrounds a central recess configured to cradle a user's head and support the cervical spine in a neutral alignment. At least two access openings are disposed on opposite sides of the outer shell, each provided with a detachable fastener. At least two C-shaped bolster inserts are dimensioned and shaped to be received within the perimetral channel face-to-face to substantially occupy the entire perimetral channel. Each bolster insert has its own detachable fastener permitting the user to independently add or remove fill material to achieve a desired loft, density, and height. Due to the permanently filled central recess, the pillow maintains its ergonomic profile regardless of fill level and is suitable for users from toddlers to adults, as well as for use as a travel pillow.