Flexible seals for process control valves are disclosed. An example disclosed seal includes a seal for use with a butterfly valve. The example seal includes a substantially flexible ring-shaped carrier configured to be moveably fixed within the butterfly valve and to surround a flow control aperture therein. The example seal includes a seal stiffener adjacent the substantially flexible ring-shaped carrier to increase the stiffness of the substantially flexible ring-shaped carrier in a first flow direction. The example seal includes a substantially rigid seal ring to engage an opposing surface.