A linear compressor includes a shell, a frame in the shell, a cylinder defining a compression space, a piston in the cylinder, a motor assembly configured to drive the piston, a discharge cover unit defining a discharge space, a discharge valve configured to selectively open and close the compression space, and a valve spring assembly configured to provide elastic force that causes the discharge valve to contact the cylinder. The discharge cover unit includes a cover housing that defines an opening configured to communicate with the discharge space, a discharge cover that inserts into the cover housing through the opening, that contacts an inner surface of the cover housing, and that covers the opening, and a fixing ring configured to be positioned at an inner surface of the discharge cover. A thermal expansion coefficient of the fixing ring is greater than that of the discharge cover.