A planar electrochemical gas sensor is provided with at least one working electrode (4), at least one counterelectrode (4″), at least one electrolyte-filled planar electrolyte carrier (10), at least one planar housing upper part (3) and at least one planar housing lower part (2). The electrodes (4, 4″) are arranged such that they are in two-dimensional contact with the electrolyte carrier (10). The housing upper part (3) and the housing lower part (2) are connected with one another such that the electrodes (4, 4″) and the electrolyte carrier (10) are pressed against one another in such a way that they are secured against displacement. The housing upper part (3) and the housing lower part (2) are partially in direct two-dimensional contact with one another, and the connection of the housing upper part (3) and the housing lower part (2) in the area of the direct two-dimensional contact is present at least along a closed figure, which surrounds the electrodes (4, 4″) and the electrolyte carrier (10).